This was a level of detail about ring generators that I didn't realize I needed in my life. I didn't expect some of these methods to be in play. I look forward to the next video!
Regarding “spinning metal”: Take it to the extreme and you get an Alexandersson alternator, used to transmit (long wave) radio. One such machine survives in working order in Grimeton in Sweden and occasionally transmit with the call sign SAQ at 17442 m.
Early in my career, I shorted out a ringing machine on the overnight shift. The backup kicked in immediately and alarms went of in the CO.As soon as my co-worker and I realized what was going on, we went to basement to see if we could fix it. Luckily for us, there was a spare unit in the basement and we scavenged parts to repair the main ringer. An hour later, we had the main ringer back online and thought we had dodged a bullet until our foreman came into the office and asked what was going on. It turns out the the backup ringer has a slightly different tone and everyone in town was calling in troubles because their phone sounded "different".
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I have been teaching technology and science in Patagonia, Argentina for more than 50 years and I so enjoyed your video. I have hope in humanity watching young people like you creating these amazing videos. You brought a smile and happiness to an old engineer. Cheers!!!
Oh, this was wonderful. Gives me a much needed perspective on what was really happening in the CO as these wonderful sounds played. It's only half the story to know how a 1XB connects calls, it's the other half to know how the machine spoke to a human, in a sense, to let us know what was going on. Incredible.
Thank you Sarah for all your videos and for sharing all the information. I’m a huge fan of Evan Doorbell’s work, and while he covers everything you hear from one side of the receiver (pun intended), you are showing the other side that we never get to see. I truly appreciate all of your (and those around you) dedication to all that you do.
Hi Sarah, really cool video. Brings me back to my first job in the telecom business as a Western Electric installer back in the early '80s at LSANCA06, a 2 MG 5xb. I was on the power crew working graveyard replacing the big 440/3p to 48 volt motor generator sets with big, honking 1000 amp ITT rectifiers (5 of them!). I was a newbie grunt (19yrs old, I think), and was fascinated by the ringing machines. I remember that they were duplicated - a 440v AC powered one, and a minus 48vdc powered one. They provided both redundancy and DC service continuity for AC outages. By that time, the tone generator itself was replaced by a precision plant, but all of the ringing and interruptions were still carried out by that cool Frankenstein RG. So many cool things in the power room back in those days. Motor operated CEMF cell switches, giant knife switches and a power room logbook that went back to the 50's (with a cool entry about the Sylmar earthquake in the early 70s). I remember that there was a separate 130 volt plus/minus plant (with it's own giant batteries) just for CxR and coin. I later went on to a long career in the PBX business with NEC and now with a software company, but my time in that power room (and the xb) was probably the most fun of my career. Thanks again for the memories!
I've been looking for videos like this for years. I'm too young to have lived in the analog telephone network era, but I love old technology and became obsessed with the Evan Doorbell recordings and learning about the Bell System. My grandfather worked for Western Electric and I have other relatives who worked elsewhere for AT&T and other telcos. I always wanted to actually learn how all that old equipment actually worked in a way more intuitive than reading through Bell System documentation written for people with a better grasp of electrical engineering than I do. These are some of the coolest and most well done videos of explaining analog technology on UA-cam and I'm so glad they exist!
I really enjoyed this video as I was charged with reviving one of these "P" type machines in Hartford, CT. The ringing machine in our toll office had a failing gearbox. so I spent a few days going through the prints of a dead step office to learn how this machine worked. There were transfer switches between the dead step office and the toll office so I knew that I would be able to get the signals to the toll office. It took a couple of weeks to get the "P" machine cleaned up and adjusted as it had been idle for almost 20 years. I installed the fuses and the "P" Machine fired up and produced a dial tone and ringing signal. A little work on the mercury drums and the cutover day came up. I threw the switches and the toll office was operating on the "P" machine. I was able to keep the toll office on the "P" machine for the entire time it took to swap out the bad gearbox in the toll office. Sadly, I had to cut back and shut down the "P" machine when the job was done. Say what you want, but that old machine could have worked for many more years if it weren't for the ESS & Digital offices. Thanks for the video.
Two of the machines we have came out of Hartford! They are newer, likely from the 1960s, and were gray instead of black, like this old one here. I believe they were manufactured by GE for Western Electric.
I went down a rabbit hole to figure out how I can connect my rotary phones for my train station. I then came across your channel, and you are an encyclopedia of knowledge on this!
Really enjoyed this video. I used to work in a 355a SxS cdo which had a 806f type of ring plant if I remember right. Then I worked a no.1 SxS toll and local switch which used the mercury type ring plant. Interesting stuff, even for a retired switchman like me. Thank you so much. This brings back good memories.
Rectifier trivia: motor-generator sets were fairly common in the computer systems of my youth, where they provided (mostly) isolation from transients on incoming power. Thus spinning-metal-things were used long after solid-state rectifiers were common (first selenium, and later silicon). The motor-generator sets for mainframe computers were AC-AC sets, and the computers themselves were using silicon diodes to rectify the AC from the motor-generator. Mercury was, once upon a much more toxic and dangerous time, a very popular solution for electrical switching without contact erosion, too.
I worked in a computer facility and we had an EPE 50 KVA 60 Hz to 60 Hz motor-generator set UPS up to about the year 2000. There was also a DC winding which was powered by (I believe it was 24) 33 amp-hour SLA batteries in series. Against my advice, my boss had the unit installed in the basement. A cast iron pipe elbow of the building’s fire sprinkler system burst and flooded the basement with 150,000 gallons of water which destroyed the UPS and shut down the computer facility temporarily. The replacement UPS from EPE was solid state as MOSFETs and IGBTs are now up to the task and inexpensive enough. The UPS foolishly was reinstalled in the basement. I suggested raising the unit on courses of blocks to get it above the water line clearly visible on the wall, but that was deemed too much bother. The business I worked for was many times more dependent on computers, but wasn’t willing to spend a few thousand Dollars to significantly reduce their risk. Go figure. The boss did pay attention to getting the backup Diesel generator and transfer switch on a biweekly test cycle. I recently toured a facility which 3D prints medical devices such as knee replacements from fused titanium powder. Their UPS system incorporated a physically rather large flywheel system manufactured by Caterpillar. I believe there was enough stored rotating energy to keep the facility up for at least a few minutes while waiting for the generator to come on line. I don’t think I’d want to be anywhere near there if anything mechanically bad ever happened!
A place I used to work at also had an MG set providing power to their mainframe (this was in the late 80's / early 90's). They also distributed that power to some of the engineers' cubicles so we could have uninterrupted power for our stone-age pc's. When I first started there, I unknowingly plugged my desk clock into that circuit. Needless to say, it didn't keep time very well, and that's how I discovered my error...
Motor generators used to be used a lot in trains as well, converting the power supplied from the loco to whatever was required in the coach for lighting, battery charging etc.
@@crabby7668 And in Elevators from the era believe it or not. A lot used those AC/DC converting things, some even used the Mercury arc stuff I don't recall the name of it.
Since this channel is about telephone exchanges, they also used Motor-Gen sets. Although, not in use when I was in the exchange, the moto-gen set had been left in the basement along with the open battery boxes. The DC brush sets of the geneerator were about 3 ft long (perhaps a little shorter). I was told that when the system was under considerable load, the arcs from the brushes were about 8 inches long - the smell of ozone!
That mercury switch concept is brilliant! I remember seeing a ringing generator once at a UK exchange, I have wondered for literally decades how they work ! Thanks :-)
I just discovered this channel and am loving it. My father worked for Bell from the 50's to the 90's. I would go along with him to work on weekends and just sit watching the step selectors and relays operating. Most centrals still used motor-generator sets at the time as well as rotary interrupters to flash indicator lamps. This technology to me is far more interesting than the latest computer automation developments of today!
I recall using pay phones in the 1970s to make long distance calls. The operator had to be involved. The operator would ask for the money before placing the call. Then the operator would stay on the line until the party answered. If the called party was busy, the operator would disconnect from the called party number and then refund the coins that were deposited. It was very loud to the ear. It sounded just like a ringtone only it was multiple times louder. I knew to hold the receiver away from my ear when this was happening. You would also hear a mechanical bang coming from inside the payphone and then you’d hear your money release down into the coin collect section. It was highly mechanical. It makes sense that the coin collect / return was powered by the ring generator equipment. It didn’t make sense in the 70s but now that you’ve explained it, I understand why it sounded like a heavily amplified ringtone now. Oh I should also mention that sometimes the coins would not return and the operator would have to initiate a coin return again and usually the second time the phone would give you back your money. Not sure why it would do that. I figured corroded parts inside the phone.
I always wondered about these "tone machines," and you satisfied a longstanding and powerful curiosity perfectly. Thank you Sarah! I can't wait to visit the Museum!
In a machine I helped design we made "precise" (busy, reorder, ring, dial) tones with a handful (12 or so, I don't remember) of integrated circuits. This was back in the late 70's when we made telephone answering service machines (to replace cord boards which were common even then!).
Fantastic job on CRDs live stream! Looks like I have a lot of videos to catch up on. I love to learn. I sincerely appreciate your ability to explain in layman’s terms, I can see the passion and knowledge and I know sometimes it can be a struggle. Thanks for the hard work!
Interesting story on the early mechanical call progress tone (dial tone, audible ringback, busy tone) generators! For about 11 years, I worked for BNR Inc., which designed equipment manufactured by Northern Telecom. I did some development work on their SL-1, later rebranded Meridian, PBX. The system was PCM (digital) internally and had a tone and digit circuit on two boards. The circuit generated the call progress and other tones by reading bits from ROM. By that time, the Bell System had adopted the precise tone plan, which specified 4 tone frequencies. Dial tone, audible ringback and busy tones were each a mix of two of those tones. The board also generated the DTMF tones and a special ringing sound, for the system's proprietary telephone sets, played through a loudspeaker in the set. I proposed to redesign the two board circuit to fit on one board as a cost reduction and to save space in the system shelves. I worked on the team which did the redesign. One interesting facet was that we made our nominal frequencies for the DTMF tones be the nearest multiple of 10 HZ. So, for example, 697 Hz became a very accurate 700 Hz. The approx. 0.43% nominal frequency offset was well within the required 1.5% tolerance. I am not aware of the nominal frequency changes creating a problem in the field. Another version of the board was designed for a version of the PBX for use in the Swedish telephone network. It generated the call progress tones used in Sweden.
Given my misspent youth in public payphone boxes, this and all Connections Museum's videos are fantastic, and it's great to find out more about the technology behind it all. Phones have been the one thing that has fascinated me all my life, and my dream job. one day, perhaps.
Great video, I love this older technology and the clever way the switching arrangement was done with the Mercury in the isolated metal discs. Your voice is awesome and enhances the topics discussed. Keep up the great videos.
Hi Sarah, Terrific work you are doing. I'm looking forward to more. You may have thought of this already but keep this in mind that when you connect up one of the big ringing machines and try listen to the audible ring coming out of it. The audible ring that we would normally hear is coming through a trunk circuit or SxS connector that puts a .04MF capacitor in the path. This significantly changes the sound . The sound of the ringing as monitored on the called line is very loud and overwhelmed by the 20HZ and 40HZ components. The capacitor reduces the volume and filters out that low frequency, giving you the nice 420HZ plus harmonics that we all know as "City Ring". --Will
Exactly right. I think it will be interesting (once we get one of these machines going) to listen to the ring at various points, with and without the caps to see how the sound is different!
"And through the magic of having 6 of them...." that's way more magic than Alec. You talking about tone wheels and musical instruments got me thinking.... you need a Telharmonium! ;)
I would love to hear what the Telharmonium sounded like. It's possibly the very first synthesizer, depending on how you look at it, and as a fan of electronic music, I'd love to own one. Too bad that it weighs over 600 tons and uses more than half a megawatt to operate.
This seems like something Fran Blanche of Frantone fame would be interested in. She has a channel on UA-cam and she's a LEGENDARY boutique pedal builder. The current version of the Big Muff was designed by, her while she worked with ElectroHarmonix X # of years ago. All of her Frantone designs were completely new circuits never used by anyone before she used them. So no "it's a version of a tube screamer" or any other pedal. These circuits didn't exist before Fran invented them 🙏 for ALL of her pedals. Anyway. She's got a really cool channel, too. You should watch it if you don't already 👌
Electronics from 100+ years ago are truly fascinating. The coolest part being you can figure out how they work just by looking at things because it's all mechanical and nothing is solid state.
Mind Blown!! You are a genius, your extensive knowledge of the mechanics and electrical characteristics of these machines plus the pure physics and durability is amazing.
I worked in a Panel office BCO/GCO where we had 2 ringing machines. 1 as a backup. we used the old tone style until precise tones became the fad with touch tone. the precise tone generator used transistorized plug in cards an a plug in frequency specific vibrating plug in. Nice video. Thanks.
As a stage crew member and the sound engineer, I've at times needed a ringing telephone. finding a source for this signal was difficult until I came across an electronic phone ringer. The voltage and frequency was performed electronically in a package about 6" square powered by a 9volt battery. Perfect for about $100.00. A unit that not only sent a ringer but hooked up several phones to actually talk is also available for about $200. Amazing, you think?
If you want to hear what the old Bell System “city tones” for dial tone, ringing, and busy signals sounded like, you can hear them on smithno41’s dial tone generator upload, and if you want to hear a sample of what the ringing signal on the Automatic Electric (independent) system sounded like, you can hear that on Veronique Laurent’s Mildred Pierce ending scene around the 3 minute mark. Also, andyvalve100’s upload of “ringing machine 44a” lets you hear what the various tones and ringing signals sounded like on a British tone generator from 1959
Nice presentation. As somebody who owned and restored a 1942 60" GE WW2 Carbon Arc searchlight with 800,000,000 CP, this shizz is definitely my kind of jam.
It looks like a Dynamotor...an ac motor driving a dc generator....or vice versa ...a dc motor driving a ac alternator. Years ago in a shop I worked in, there was an old radio that had a Dynamotor inside for high voltage DC. The speed of an alternator sets the frequency/tone. Vacuum tubes have been around since the 1890s, but weren't really reliable until the '30s.. There were mechanical radio transmitters..alternators and spinning spark gaps ...that transmit audio. Not the best quality, but there were half million watt transmitters that used this back in the day. There was a " howler tone" to let you know the phone was off the hook. Years ago, I lived near a dump, and the phone company threw out 45 volt batteries that still had life in them, great for vacuum tube projects. This is a great video!
I used to routine the ringing interrupter on the 12th floor of the Chicago 1 office. We used crocus cloth to polish the snot out of the commutators but about once a month we'd get calls that they weren't working. One day I opened the BSP and read that we were to only buff the commutators with a ouece if twill cloth wrapped sround a stick. The commutators oxidized but never failed after that.
This answers so many questions I've had on how tones were generated. thanks so much! Seriously appreciate the way this is presented. Also caught the CISCO logo at 9:57, neat!!
Thank you Sarah. When I was a kid in the 1960s, our local Bell System office held n open house. Our office served, I’m estimating, 10,000 subscriber lines and pay stations as well as being a long lines repeater facility. The building comprised three stories plus basement, about 100 ft on a side. The top floor was operator consoles, billing recorders, long lines TV transmission monitoring equipment and test desks. Somewhere around 1/3 to 1/2 of the second floor was amplifiers with large vacuum tubes, carrier current modulators and demodulators, the rest was racks of SxS frames. My recollection was the first floor was almost all SxS frames and main distribution frame where subscriber loops terminated. The basement had a row of ring generators with large black motors. It seemed like they were physically larger than the P type shown here (possibly faulty memory from 60 years ago). There were tone generators present because we had the more melodic versus raspy call progress tones. The rest of the basement contained enormous glass cased 2 Volt cells connected to yield the -48 VDC plant voltage. I thought it was odd to put the power source in a basement where it would be damaged if there were a flood. The office is on fairly high ground, so I suppose that was a calculated choice. At least any noxious fumes where not likely to permeate the floors where switching equipment and electronics resided. The office was modernized to electronic equipment in 1976, most likely a mid generation ESS. I do not know what is in there now, as that area is now part of the so-called Uverse where a lot of capability is decentralized into cream colored cabinets scattered throughout neighborhoods.
Those old lead acid batteries were incredibly heavy. It wouldn't surprise me if the high floor loading was one of the reason to put them in the basement, although all of the other stuff appears pretty heavy too.
Very interesting to see how it is done in the US. I worked as a Telephone Technician in NZ in the 80's. The continuous tone was generated much the same but the interrupted tone was from a bank of cam wheels that provided the ring cadence and the other tones N.U.T (number unobtainable tone) Busy tone and various timing pulses required in a Step x Step exchange. Thank you for the info.
Thanks! Yes, there are other systems in the US that also use cam wheels. The ringing machine we are running on currently works that way. The XY system by Automatic Electric has some interrupter cams that are quite large and fascinating to watch.
Interesting that you brought up the coin voltage @3:55 in the video. There were 2 way to phreak at a payphone. One was using a tone generator device called a Rad box. And the other way was to get access to the phones TNI box and splice into the coin control wire (usually a yellow or purple colored wire.) a rectifier diode. Depending on the orientation of how the diode is install. This would disable ether the return or collect control of the payphone. I was never good at redboxing and would always get a live operator in the middle of my conversation and would have to hang up or otherwise, keep some change around so I could put real money into the phone while the operator was on because she could tell if you tried using your redbox on her. Anyways, by putting that diode in the coin circuit. Any money that I had to put into the phone because I screwed up the redbox I would get back at the end of the conversation. If course, if you wanted to be a real jerk. You could put the diode in the other way and make the phone eat everyone money. I really miss those days. it was a lot of fun to mess around with the phone system back then.
Wonderful, Sarah! Well done! Thank you. Glad you provided the sounds. Very surprised abouthe use of Hg. To ring a garage sale-purchased extension phone without getting caught by Mountain Bell, I placed a larger neon bulb in series withe ring coil. (Would NE-2 have conducted enough amperage?) The ring voltage would break down theon and ring the bell. When Mountain Bell would testhe line, the additional bell coil was not detected. When I bought a telephone answering machine, I reported its *0.5* Ringer Equivalency as *2.5* . This enabled me to have two additional unmolested telephones on the residentialine.
@@ConnectionsMuseum Mountain Bell charging for a customer-supplied extension telephone seemed improper. The *Ericsson* Ericophon Cobra phone stood upright on its base. The base contained the rotary dial. The telephone would hang up when set on its base. It had a neon bulb which would flicker from the ring voltage. Always wondered if that was to make the telephone undetectable. But it had an electronic ringer so probably a very small Ringer Equivalency.
You're welcome! We really should get going with the Patreon so folks could donate. In the meantime, if you'd like to contribute to the coffee/beer fund, you can paypal us at info@connectionsmuseum.org
I'm just a mega nerd for everything that has wires, this channel is utterly brilliant 😍. Dont know what part I liked the most, let me choose the 🎸 section to explain tone generation 🤣
I try to learn something completely different and new everyday. You nailed it. Your videos are amazing. I imagine with your electro-mechanical aptitude that you will one day invent something important and it will be essential for everyday communications. Best wishes and success on preserving and maintaining our communication history.
Absolutely fascinating! I had no idea how those tones were created. Simply ingenious! Thank you for creating these videos and for preserving all of this amazing equipment!
Thank you for making this video you did a great job on your script and presentation. I love the electromechanical solution for a problem, The wired Bell network of our nation had redundancy and would work regardless of our electrical grid and other factors unlike today's cellular network. More Please, how about the Battery board?
Sarah, If you were to check with the older, more experienced machinists in your area, you might be able to find one that can properly align that cast... casting lol and weld it back together. Yes, cast iron can be welded, brazed, etc together but it takes the correct process especially with a chunk of that size. Thanks for the amazing history on these machines! I remember some of these sounds when I was a kid, and always wondered why they were different, and why one system had the different sounds. I lived in a rural area back then, so there were a few different systems that could be heard locally, and then there's the long distance calls.... woot! Thanks again for the great vids!
I hired on with Southern Bell in 1962....Later changed to Bell South for 38 years....I worked the step office, #5 Crossbar then electronic toll....I liked #5 Cross bar best of all....
It might be interesting to other viewers that these ringing machines were used in many central offices well into the 1970’s and 80’s. I saw a great many P type machines running in central offices during that time frame. I was not aware of the use of the brush type ring back generator, but I do recall hearing that rough ring back tone when calling some rural areas. Excellent videos! I want to plan a visit to your museum.
I worked in a communication center that was built in the 1960s and continued to use that technology. In the relay room was a ring tone generator. A couple of things I noticed were that the ring forward signal was higher powered than the ring back signal because the ring forward signal had to activate the bells on the receiver whereas the ring back signal only had to produce tone in the earpiece of the caller. The second thing I noticed was that the generator alternated between generating a ring forward signal and a ring back signal. So when the caller heard nothing the phone the other end was ringing and when the caller heard ring back, the phone being called was silent. I was told this was to reduce the fluctuations in the power drain on our DC voltage system.
I have no idea why, but the high-five after putting the ringing machine on the table cracks me up. Also, at 8:06 with the gitfiddle, I call band name "Linefinder". 🙂
Wow! I've always wondered how these sounds were made. I'm 80 now, and as a child, in visits to grandma's house (a very small town in Kansas) I saw the wall-mounted wooded box with the handle on the side. Turn it, and the switchboard answered, whereupon you'd tell her who you wanted to talk to, and she'd hook you up. Later, things were upgraded, and grandma got a number -- Red32. Then we got the round dials with the holes in them, and miraculously the touch-tone arrived sometime in the early 60's. There were several things to like about those wired phones: they were comfortable to hold and use, they ALWAYS worked, and the sound was excellent, or at least very clear and understandable. Now of course a smart phone rides around in my pocket so I have a phone everywhere. But it's an ergonomic nightmare, has atrocious sound, frequently breaks up, and here in West Texas, stops working altogether at the drop of a hat. So, in some ways it's better, but in others a definite step down from the not-so-good-ol days. Great series. I'm really glad to have found it!
I was able to see a more modern version of this machine actually operating inside a working telephone exchange. The machine I saw was still mostly mechanical but was a more advanced version which occupied only about as much space as one of the electric motors in the machine shown in the video. Actually, less space, since it had a smaller diameter. There were actually two machines, in case one failed or required maintenance, so the tones would continue without interruption. The machine generated two basic tones. If I remember correctly, they were 25Hz and 600Hz. The 25Hz was used to provide the ring current for the ringer, the 600Hz was used to provide the busy tone and congestion tone and the two were mixed together in order to provide the characteristic dial tone and when interrupted, ring tone. Of course this was in Australia where the tones are slightly different to the American tones. The machine also provided all of the mixing and the appropriate interruptions. Modern amplification methods meant that the machine didn't have to handle huge currents and so could be smaller than older machines.
I always find it interesting learning how technical features were implemented years ago. I had not thought about how the other telephone tones were produced. Contrast this rotary ring generator with the fiber ONT (optical network termination) I have for internet and to emulate legacy POTS. The ONT is about the size of a 3x5 index card and about 1/2 inch thick. Beside all the internet stuff it provides the Central Office BORSCHT (battery, overvoltage protection, ringing, signaling, coding, hybrid and test) functionality. As amazing as my little ONT is I doubt any will survive 100 years to live on in a museum.
I study OTR (old time radio) shows, and direct & perform in recreations of them. One thing I've noticed in the original OTR shows is that the telephone tones and dialling pulses sound lower and more clicky than the modern tones of the 1970s onward. To make my recreations sound more authentic, I use the old telephone sound effects.
Hi Sarah, At some point, would you please do a video about the various sounds generated from the time of the ring generator to current day, and what they meant - things like "reorder" throughout the years, and the (I'm not sure what they're actually called) 3-tone signals? I've been watching these videos for quite a while, and at some point, I need to get off my butt and come take the tour. Thanks for the work you put in to your videos, and keeping the working history of something we take for granted alive.
HAMMOND B3! WOOOO! My favorite band had a B3 as a permanent part of the band. They also were the first rock band to use 2 drummers, which was picked up by their lead guitarist from James Brown.... Figured it out? The Allman Brothers Band! 🙏👌🎸
Came across this video due to a friend linking it but remember you from a video I saw years ago. glad to find you here and subscribe! I loved the mercury switch; it reminds me of the tilt bulb ones I worked with in various devices but turning the idea around.
420 reference ..i dig it ..i am surprised none of the tones are at 440 mhz like the guitar ..i gots to admire the boomer generation and older for their amazing engineering that built this country ..my question is ..where did all the billing take place ..was there a machine that did that ..idk ...great videos and well presented ya'all :)
I have a question about the changeover process of this from old to new. I grew up in Spanish Fork, Utah, and I specifically remember these wheel-tones being our ring-back and dial tones, and you or Evan told us somewhere that these almost always came with a crossbar 5, so I guess that that's what Spanish fork started with, maybe back in the '50s or '60s, with the prefix of 798 (with Utah's 801 area code). I only remember back to the mid/late 70s though. Our dial tone was sounding pretty crappy in the late 80s. Oddly enough, not only had it gotten fairly crackly, but I think I even remember the frequency having little bursts of slowing periodically. But I can't remember that for sure. One day in October 1990, I picked up a phone and heard a NEW dial tone, and it was _clean,_ like a brand-new machine was making it! It sounded like the one that Provo and similarly bigger cities around had already been using since I was ever aware, like back in the 70s, and I was like, "HUH, now WE have this!" I dialed out and sure enough, it sounded just like ring-out did when I called somewhat bigger cities like Provo, Orem, or Salt Lake City! And then I wondered what the changeover was like! So even now I wonder what it would have sounded like if I had picked up the phone overnight right while they were turning the old tone machine off, disconnecting it, and then turning the new one on. Do you think I would have just heard the last of the old tone, some clicks, blanking, more clicks, and then the new tone, because they plugged it over before turning the motor off, or do you think I would have heard the old tone wind down to a stop because they left it in circuit while they turned it off, and then some clicks, blank, clicks and the new tone immediately on because it's solid-state instead of rotary?
Those interrupters are particularly clever little things aren't they, so simple in their design and yet rather effective at the task required. Certainly beats regularly burning out contacts if they were to have used cams or constantly polishing your ring as with the older systems. Thank you for another really interesting video Sarah, I'm already eager for the next installment! (P.S. Were you responsible for the graffiti?! 😄 )
I used to enjoy working in the power room (4000A -48VDC, ±130VDC, -24VDC, and IIRC there was a small converter for some sort of 36 volt use). Polished a whole lot of commutators and slip rings in my day. 😀
Sarah; thanks for another very informative video. The concept of 'city ring' gave me a laugh. Had not thought about it, but understand how that phase developed. I also remember the startling change to the call progress tones, with the cut over to ESS. How does the 20Hz ring output waveform, of this machine compare with the old hand crank magneto and electronic ring plant that replaced these rotating machines?
“Through the magic of having six of them … “ I see you there 😂
😉 hello technology connections fan
I found this channel days ago and have not stopped watching. Sadly I am 9000kmts away from the museum but I REALLY want to visit....
This was a level of detail about ring generators that I didn't realize I needed in my life. I didn't expect some of these methods to be in play. I look forward to the next video!
Glad you enjoyed it!
The Mercury incased interrupters were genius!
In every video you astound me with the deep details you dive into.
Regarding “spinning metal”:
Take it to the extreme and you get an Alexandersson alternator, used to transmit (long wave) radio. One such machine survives in working order in Grimeton in Sweden and occasionally transmit with the call sign SAQ at 17442 m.
Early in my career, I shorted out a ringing machine on the overnight shift. The backup kicked in immediately and alarms went of in the CO.As soon as my co-worker and I realized what was going on, we went to basement to see if we could fix it. Luckily for us, there was a spare unit in the basement and we scavenged parts to repair the main ringer. An hour later, we had the main ringer back online and thought we had dodged a bullet until our foreman came into the office and asked what was going on. It turns out the the backup ringer has a slightly different tone and everyone in town was calling in troubles because their phone sounded "different".
I have been teaching technology and science in Patagonia, Argentina for more than 50 years and I so enjoyed your video. I have hope in humanity watching young people like you creating these amazing videos. You brought a smile and happiness to an old engineer. Cheers!!!
Oh, this was wonderful. Gives me a much needed perspective on what was really happening in the CO as these wonderful sounds played. It's only half the story to know how a 1XB connects calls, it's the other half to know how the machine spoke to a human, in a sense, to let us know what was going on.
Incredible.
Thank you Sarah for all your videos and for sharing all the information. I’m a huge fan of Evan Doorbell’s work, and while he covers everything you hear from one side of the receiver (pun intended), you are showing the other side that we never get to see. I truly appreciate all of your (and those around you) dedication to all that you do.
Hi Sarah, really cool video. Brings me back to my first job in the telecom business as a Western Electric installer back in the early '80s at LSANCA06, a 2 MG 5xb. I was on the power crew working graveyard replacing the big 440/3p to 48 volt motor generator sets with big, honking 1000 amp ITT rectifiers (5 of them!). I was a newbie grunt (19yrs old, I think), and was fascinated by the ringing machines. I remember that they were duplicated - a 440v AC powered one, and a minus 48vdc powered one. They provided both redundancy and DC service continuity for AC outages. By that time, the tone generator itself was replaced by a precision plant, but all of the ringing and interruptions were still carried out by that cool Frankenstein RG. So many cool things in the power room back in those days. Motor operated CEMF cell switches, giant knife switches and a power room logbook that went back to the 50's (with a cool entry about the Sylmar earthquake in the early 70s). I remember that there was a separate 130 volt plus/minus plant (with it's own giant batteries) just for CxR and coin. I later went on to a long career in the PBX business with NEC and now with a software company, but my time in that power room (and the xb) was probably the most fun of my career. Thanks again for the memories!
This was a fascinating read.
Its a man, not a sarah.
I've been looking for videos like this for years. I'm too young to have lived in the analog telephone network era, but I love old technology and became obsessed with the Evan Doorbell recordings and learning about the Bell System. My grandfather worked for Western Electric and I have other relatives who worked elsewhere for AT&T and other telcos. I always wanted to actually learn how all that old equipment actually worked in a way more intuitive than reading through Bell System documentation written for people with a better grasp of electrical engineering than I do. These are some of the coolest and most well done videos of explaining analog technology on UA-cam and I'm so glad they exist!
I really enjoyed this video as I was charged with reviving one of these "P" type machines in Hartford, CT. The ringing machine in our toll office had a failing gearbox. so I spent a few days going through the prints of a dead step office to learn how this machine worked. There were transfer switches between the dead step office and the toll office so I knew that I would be able to get the signals to the toll office. It took a couple of weeks to get the "P" machine cleaned up and adjusted as it had been idle for almost 20 years. I installed the fuses and the "P" Machine fired up and produced a dial tone and ringing signal. A little work on the mercury drums and the cutover day came up. I threw the switches and the toll office was operating on the "P" machine. I was able to keep the toll office on the "P" machine for the entire time it took to swap out the bad gearbox in the toll office. Sadly, I had to cut back and shut down the "P" machine when the job was done. Say what you want, but that old machine could have worked for many more years if it weren't for the ESS & Digital offices. Thanks for the video.
Two of the machines we have came out of Hartford! They are newer, likely from the 1960s, and were gray instead of black, like this old one here. I believe they were manufactured by GE for Western Electric.
@@ConnectionsMuseum I wonder if you have my old friend!
I went down a rabbit hole to figure out how I can connect my rotary phones for my train station. I then came across your channel, and you are an encyclopedia of knowledge on this!
Really enjoyed this video. I used to work in a 355a SxS cdo which had a 806f type of ring plant if I remember right. Then I worked a no.1 SxS toll and local switch which used the mercury type ring plant. Interesting stuff, even for a retired switchman like me. Thank you so much. This brings back good memories.
Rectifier trivia: motor-generator sets were fairly common in the computer systems of my youth, where they provided (mostly) isolation from transients on incoming power. Thus spinning-metal-things were used long after solid-state rectifiers were common (first selenium, and later silicon). The motor-generator sets for mainframe computers were AC-AC sets, and the computers themselves were using silicon diodes to rectify the AC from the motor-generator. Mercury was, once upon a much more toxic and dangerous time, a very popular solution for electrical switching without contact erosion, too.
I worked in a computer facility and we had an EPE 50 KVA 60 Hz to 60 Hz motor-generator set UPS up to about the year 2000. There was also a DC winding which was powered by (I believe it was 24) 33 amp-hour SLA batteries in series. Against my advice, my boss had the unit installed in the basement. A cast iron pipe elbow of the building’s fire sprinkler system burst and flooded the basement with 150,000 gallons of water which destroyed the UPS and shut down the computer facility temporarily. The replacement UPS from EPE was solid state as MOSFETs and IGBTs are now up to the task and inexpensive enough. The UPS foolishly was reinstalled in the basement. I suggested raising the unit on courses of blocks to get it above the water line clearly visible on the wall, but that was deemed too much bother. The business I worked for was many times more dependent on computers, but wasn’t willing to spend a few thousand Dollars to significantly reduce their risk. Go figure. The boss did pay attention to getting the backup Diesel generator and transfer switch on a biweekly test cycle.
I recently toured a facility which 3D prints medical devices such as knee replacements from fused titanium powder. Their UPS system incorporated a physically rather large flywheel system manufactured by Caterpillar. I believe there was enough stored rotating energy to keep the facility up for at least a few minutes while waiting for the generator to come on line. I don’t think I’d want to be anywhere near there if anything mechanically bad ever happened!
A place I used to work at also had an MG set providing power to their mainframe (this was in the late 80's / early 90's). They also distributed that power to some of the engineers' cubicles so we could have uninterrupted power for our stone-age pc's. When I first started there, I unknowingly plugged my desk clock into that circuit. Needless to say, it didn't keep time very well, and that's how I discovered my error...
Motor generators used to be used a lot in trains as well, converting the power supplied from the loco to whatever was required in the coach for lighting, battery charging etc.
@@crabby7668 And in Elevators from the era believe it or not. A lot used those AC/DC converting things, some even used the Mercury arc stuff I don't recall the name of it.
Since this channel is about telephone exchanges, they also used Motor-Gen sets. Although, not in use when I was in the exchange, the moto-gen set had been left in the basement along with the open battery boxes. The DC brush sets of the geneerator were about 3 ft long (perhaps a little shorter). I was told that when the system was under considerable load, the arcs from the brushes were about 8 inches long - the smell of ozone!
That mercury switch concept is brilliant!
I remember seeing a ringing generator once at a UK exchange, I have wondered for literally decades how they work ! Thanks :-)
Sarah, than you so much for your videos! it always a pleasure watch and learning from you; you are a great teacher!
I just discovered this channel and am loving it. My father worked for Bell from the 50's to the 90's. I would go along with him to work on weekends and just sit watching the step selectors and relays operating. Most centrals still used motor-generator sets at the time as well as rotary interrupters to flash indicator lamps. This technology to me is far more interesting than the latest computer automation developments of today!
"*nice" :)
this is fascinating, captivating presentation Sarah and co
I recall using pay phones in the 1970s to make long distance calls. The operator had to be involved. The operator would ask for the money before placing the call. Then the operator would stay on the line until the party answered. If the called party was busy, the operator would disconnect from the called party number and then refund the coins that were deposited. It was very loud to the ear. It sounded just like a ringtone only it was multiple times louder. I knew to hold the receiver away from my ear when this was happening. You would also hear a mechanical bang coming from inside the payphone and then you’d hear your money release down into the coin collect section. It was highly mechanical. It makes sense that the coin collect / return was powered by the ring generator equipment. It didn’t make sense in the 70s but now that you’ve explained it, I understand why it sounded like a heavily amplified ringtone now. Oh I should also mention that sometimes the coins would not return and the operator would have to initiate a coin return again and usually the second time the phone would give you back your money. Not sure why it would do that. I figured corroded parts inside the phone.
I always wondered about these "tone machines," and you satisfied a longstanding and powerful curiosity perfectly. Thank you Sarah! I can't wait to visit the Museum!
Outstanding presentation! I had no idea the phones were so complicated!
In a machine I helped design we made "precise" (busy, reorder, ring, dial) tones with a handful (12 or so, I don't remember) of integrated circuits. This was back in the late 70's when we made telephone answering service machines (to replace cord boards which were common even then!).
Fantastic job on CRDs live stream! Looks like I have a lot of videos to catch up on. I love to learn. I sincerely appreciate your ability to explain in layman’s terms, I can see the passion and knowledge and I know sometimes it can be a struggle. Thanks for the hard work!
Oh, the rare and lovely sight of Sarah playing a Strat in the exchange office.
And both of you lifting the machine. Girl power!
😊 thank you
Sarah, you’ve got very interesting things to say about history of telephone 🙂👍 Greetings from Poland 👋
Interesting story on the early mechanical call progress tone (dial tone, audible ringback, busy tone) generators! For about 11 years, I worked for BNR Inc., which designed equipment manufactured by Northern Telecom. I did some development work on their SL-1, later rebranded Meridian, PBX. The system was PCM (digital) internally and had a tone and digit circuit on two boards. The circuit generated the call progress and other tones by reading bits from ROM. By that time, the Bell System had adopted the precise tone plan, which specified 4 tone frequencies. Dial tone, audible ringback and busy tones were each a mix of two of those tones. The board also generated the DTMF tones and a special ringing sound, for the system's proprietary telephone sets, played through a loudspeaker in the set.
I proposed to redesign the two board circuit to fit on one board as a cost reduction and to save space in the system shelves. I worked on the team which did the redesign. One interesting facet was that we made our nominal frequencies for the DTMF tones be the nearest multiple of 10 HZ. So, for example, 697 Hz became a very accurate 700 Hz. The approx. 0.43% nominal frequency offset was well within the required 1.5% tolerance. I am not aware of the nominal frequency changes creating a problem in the field.
Another version of the board was designed for a version of the PBX for use in the Swedish telephone network. It generated the call progress tones used in Sweden.
Cool Video. Your guitar performance was unexpected and brought me much joy 😊
Given my misspent youth in public payphone boxes, this and all Connections Museum's videos are fantastic, and it's great to find out more about the technology behind it all. Phones have been the one thing that has fascinated me all my life, and my dream job. one day, perhaps.
Great video, I love this older technology and the clever way the switching arrangement was done with the Mercury in the isolated metal discs. Your voice is awesome and enhances the topics discussed. Keep up the great videos.
Hi Sarah, Terrific work you are doing. I'm looking forward to more. You may have thought of this already but keep this in mind that when you connect up one of the big ringing machines and try listen to the audible ring coming out of it. The audible ring that we would normally hear is coming through a trunk circuit or SxS connector that puts a .04MF capacitor in the path. This significantly changes the sound . The sound of the ringing as monitored on the called line is very loud and overwhelmed by the 20HZ and 40HZ components. The capacitor reduces the volume and filters out that low frequency, giving you the nice 420HZ plus harmonics that we all know as "City Ring". --Will
Exactly right. I think it will be interesting (once we get one of these machines going) to listen to the ring at various points, with and without the caps to see how the sound is different!
"And through the magic of having 6 of them...." that's way more magic than Alec.
You talking about tone wheels and musical instruments got me thinking.... you need a Telharmonium! ;)
I would love to hear what the Telharmonium sounded like. It's possibly the very first synthesizer, depending on how you look at it, and as a fan of electronic music, I'd love to own one. Too bad that it weighs over 600 tons and uses more than half a megawatt to operate.
@@josugambee3701 Somebody made an electronic emulation of it to see how it sounds.
Oh my goodness yes.
This seems like something Fran Blanche of Frantone fame would be interested in. She has a channel on UA-cam and she's a LEGENDARY boutique pedal builder. The current version of the Big Muff was designed by, her while she worked with ElectroHarmonix X # of years ago. All of her Frantone designs were completely new circuits never used by anyone before she used them. So no "it's a version of a tube screamer" or any other pedal. These circuits didn't exist before Fran invented them 🙏 for ALL of her pedals.
Anyway. She's got a really cool channel, too. You should watch it if you don't already 👌
hello fellow fran enjoyer!
Amazing technology and the presenter really knows her stuff.
Electronics from 100+ years ago are truly fascinating. The coolest part being you can figure out how they work just by looking at things because it's all mechanical and nothing is solid state.
Mind Blown!! You are a genius, your extensive knowledge of the mechanics and electrical characteristics of these machines plus the pure physics and durability is amazing.
Your ability to explain is awesome.
Your narration style and the 'steadycam' video make watching this great channel a pleasure, thanks for taking the time to share.
Amazing level of mechanical complexity to accomplish something which one would so easily take for granted! Thanks again for a superb video.
Love all your telephone systems history. your wealth of knowledge and passion on this topic is mind blowing
6:15 Technology Connections would be proud
I worked in a Panel office BCO/GCO where we had 2 ringing machines. 1 as a backup. we used the old tone style until precise tones became the fad with touch tone. the precise tone generator used transistorized plug in cards an a plug in frequency specific vibrating plug in. Nice video. Thanks.
Are you Boomer from Davenport CO??? We were good friends and you were a genius!
@@linxj6 Boomer and Ratso yes. Retired now but active with computers and writing software. Unix/Linux. Who is this?? 🤔
@@linxj6 Hi. Yes. Who is this? Joe, Jim ?
The mercury interrupter disk was a very clever design. An automatic rotary mercury switch.
I'd like to see more videos of Sarah playing the electric guitar within the aisles of an electromechanical switching office!!
The one nice thing about playing in the museum is that I get to turn it up as loud as I want :)
@@ConnectionsMuseum All the way to 11, I hope! 8o)
As a stage crew member and the sound engineer, I've at times needed a ringing telephone. finding a source for this signal was difficult until I came across an electronic phone ringer. The voltage and frequency was performed electronically in a package about 6" square powered by a 9volt battery. Perfect for about $100.00. A unit that not only sent a ringer but hooked up several phones to actually talk is also available for about $200. Amazing, you think?
Thanks for adding actual captions for the Deaf and a clear, interesting explaination
If you want to hear what the old Bell System “city tones” for dial tone, ringing, and busy signals sounded like, you can hear them on smithno41’s dial tone generator upload, and if you want to hear a sample of what the ringing signal on the Automatic Electric (independent) system sounded like, you can hear that on Veronique Laurent’s Mildred Pierce ending scene around the 3 minute mark.
Also, andyvalve100’s upload of “ringing machine 44a” lets you hear what the various tones and ringing signals sounded like on a British tone generator from 1959
Nice presentation. As somebody who owned and restored a 1942 60" GE WW2 Carbon Arc searchlight with 800,000,000 CP, this shizz is definitely my kind of jam.
It looks like a Dynamotor...an ac motor driving a dc generator....or vice versa ...a dc motor driving a ac alternator. Years ago in a shop I worked in, there was an old radio that had a Dynamotor inside for high voltage DC.
The speed of an alternator sets the frequency/tone.
Vacuum tubes have been around since the 1890s, but weren't really reliable until the '30s..
There were mechanical radio transmitters..alternators and spinning spark gaps ...that transmit audio. Not the best quality, but there were half million watt transmitters that used this back in the day.
There was a " howler tone" to let you know the phone was off the hook.
Years ago, I lived near a dump, and the phone company threw out 45 volt batteries that still had life in them, great for vacuum tube projects.
This is a great video!
I used to routine the ringing interrupter on the 12th floor of the Chicago 1 office. We used crocus cloth to polish the snot out of the commutators but about once a month we'd get calls that they weren't working. One day I opened the BSP and read that we were to only buff the commutators with a ouece if twill cloth wrapped sround a stick. The commutators oxidized but never failed after that.
This answers so many questions I've had on how tones were generated. thanks so much! Seriously appreciate the way this is presented.
Also caught the CISCO logo at 9:57, neat!!
Thank you Sarah. When I was a kid in the 1960s, our local Bell System office held n open house. Our office served, I’m estimating, 10,000 subscriber lines and pay stations as well as being a long lines repeater facility. The building comprised three stories plus basement, about 100 ft on a side. The top floor was operator consoles, billing recorders, long lines TV transmission monitoring equipment and test desks. Somewhere around 1/3 to 1/2 of the second floor was amplifiers with large vacuum tubes, carrier current modulators and demodulators, the rest was racks of SxS frames. My recollection was the first floor was almost all SxS frames and main distribution frame where subscriber loops terminated. The basement had a row of ring generators with large black motors. It seemed like they were physically larger than the P type shown here (possibly faulty memory from 60 years ago). There were tone generators present because we had the more melodic versus raspy call progress tones. The rest of the basement contained enormous glass cased 2 Volt cells connected to yield the -48 VDC plant voltage. I thought it was odd to put the power source in a basement where it would be damaged if there were a flood. The office is on fairly high ground, so I suppose that was a calculated choice. At least any noxious fumes where not likely to permeate the floors where switching equipment and electronics resided. The office was modernized to electronic equipment in 1976, most likely a mid generation ESS. I do not know what is in there now, as that area is now part of the so-called Uverse where a lot of capability is decentralized into cream colored cabinets scattered throughout neighborhoods.
Those old lead acid batteries were incredibly heavy. It wouldn't surprise me if the high floor loading was one of the reason to put them in the basement, although all of the other stuff appears pretty heavy too.
@@mfbfreak Excellent point. Those batteries were about the size of the old style trash container and there were a lot of batteries.
Very interesting to see how it is done in the US.
I worked as a Telephone Technician in NZ in the 80's. The continuous tone was generated much the same but the interrupted tone was from a bank of cam wheels that provided the ring cadence and the other tones N.U.T (number unobtainable tone) Busy tone and various timing pulses required in a Step x Step exchange.
Thank you for the info.
Thanks! Yes, there are other systems in the US that also use cam wheels. The ringing machine we are running on currently works that way. The XY system by Automatic Electric has some interrupter cams that are quite large and fascinating to watch.
You are an amazing engineer. This is going to be forgotten knowledge if we don't preserve it.
Thank you. I don't think of myself as particularly smart, but I am happy to keep the machines running smoothly :)
@@ConnectionsMuseum A year on and you still ROCK.... Thanks for being you :)
Interesting that you brought up the coin voltage @3:55 in the video. There were 2 way to phreak at a payphone. One was using a tone generator device called a Rad box. And the other way was to get access to the phones TNI box and splice into the coin control wire (usually a yellow or purple colored wire.) a rectifier diode. Depending on the orientation of how the diode is install. This would disable ether the return or collect control of the payphone. I was never good at redboxing and would always get a live operator in the middle of my conversation and would have to hang up or otherwise, keep some change around so I could put real money into the phone while the operator was on because she could tell if you tried using your redbox on her. Anyways, by putting that diode in the coin circuit. Any money that I had to put into the phone because I screwed up the redbox I would get back at the end of the conversation. If course, if you wanted to be a real jerk. You could put the diode in the other way and make the phone eat everyone money. I really miss those days. it was a lot of fun to mess around with the phone system back then.
Oh wow.
Wonderful, Sarah! Well done! Thank you. Glad you provided the sounds. Very surprised abouthe use of Hg.
To ring a garage sale-purchased extension phone without getting caught by Mountain Bell, I placed a larger neon bulb in series withe ring coil.
(Would NE-2 have conducted enough amperage?)
The ring voltage would break down theon and ring the bell. When Mountain Bell would testhe line, the additional bell coil was not detected.
When I bought a telephone answering machine, I reported its *0.5* Ringer Equivalency as *2.5* . This enabled me to have two additional unmolested telephones on the residentialine.
Reporting the REN as being higher... very sneaky ;)
@@ConnectionsMuseum Mountain Bell charging for a customer-supplied extension telephone seemed improper. The *Ericsson* Ericophon Cobra phone stood upright on its base. The base contained the rotary dial. The telephone would hang up when set on its base. It had a neon bulb which would flicker from the ring voltage. Always wondered if that was to make the telephone undetectable. But it had an electronic ringer so probably a very small Ringer Equivalency.
Thank You both so much for this channel and making these videos! Do you all have a way to buy y'all a coffee or beer? Kat
You're welcome! We really should get going with the Patreon so folks could donate. In the meantime, if you'd like to contribute to the coffee/beer fund, you can paypal us at info@connectionsmuseum.org
I'm just a mega nerd for everything that has wires, this channel is utterly brilliant 😍.
Dont know what part I liked the most, let me choose the 🎸 section to explain tone generation 🤣
This is so cool! And you're so lucky to be able to play with all of this as a job! 😍
I've seen a number of your videos just recently, and they are so great. You're an excellent presenter!
I try to learn something completely different and new everyday.
You nailed it. Your videos are amazing.
I imagine with your electro-mechanical aptitude that you will one day invent something important and it will be essential for everyday communications.
Best wishes and success on preserving and maintaining our communication history.
respect... for breaking this down for the next gen
Absolutely fascinating! I had no idea how those tones were created. Simply ingenious! Thank you for creating these videos and for preserving all of this amazing equipment!
Magneto, you're hired.
Thank you for making this video you did a great job on your script and presentation.
I love the electromechanical solution for a problem, The wired Bell network of our nation
had redundancy and would work regardless of our electrical grid and other factors unlike
today's cellular network. More Please, how about the Battery board?
Sarah, If you were to check with the older, more experienced machinists in your area, you might be able to find one that can properly align that cast... casting lol and weld it back together. Yes, cast iron can be welded, brazed, etc together but it takes the correct process especially with a chunk of that size.
Thanks for the amazing history on these machines! I remember some of these sounds when I was a kid, and always wondered why they were different, and why one system had the different sounds. I lived in a rural area back then, so there were a few different systems that could be heard locally, and then there's the long distance calls.... woot!
Thanks again for the great vids!
I hired on with Southern Bell in 1962....Later changed to Bell South for 38 years....I worked the step office, #5 Crossbar then electronic toll....I liked #5 Cross bar best of all....
Whats incredible is modern LTE networks still accept AT commands created in 1981.
That was a really good explanation of a specialized, intricate device. Clear and well paced. Thank you.
It might be interesting to other viewers that these ringing machines were used in many central offices well into the 1970’s and 80’s. I saw a great many P type machines running in central offices during that time frame.
I was not aware of the use of the brush type ring back generator, but I do recall hearing that rough ring back tone when calling some rural areas.
Excellent videos! I want to plan a visit to your museum.
Did you pull a technology connections with the phrase “with the magic of having _____ of them” 😂
I worked in a communication center that was built in the 1960s and continued to use that technology. In the relay room was a ring tone generator. A couple of things I noticed were that the ring forward signal was higher powered than the ring back signal because the ring forward signal had to activate the bells on the receiver whereas the ring back signal only had to produce tone in the earpiece of the caller. The second thing I noticed was that the generator alternated between generating a ring forward signal and a ring back signal. So when the caller heard nothing the phone the other end was ringing and when the caller heard ring back, the phone being called was silent. I was told this was to reduce the fluctuations in the power drain on our DC voltage system.
I have no idea why, but the high-five after putting the ringing machine on the table cracks me up. Also, at 8:06 with the gitfiddle, I call band name "Linefinder". 🙂
This is fascinating! And the explanation is clear, detailed and very entertaining, thanks y'all for the wonderful job you do!
Wow! I've always wondered how these sounds were made. I'm 80 now, and as a child, in visits to grandma's house (a very small town in Kansas) I saw the wall-mounted wooded box with the handle on the side. Turn it, and the switchboard answered, whereupon you'd tell her who you wanted to talk to, and she'd hook you up. Later, things were upgraded, and grandma got a number -- Red32. Then we got the round dials with the holes in them, and miraculously the touch-tone arrived sometime in the early 60's. There were several things to like about those wired phones: they were comfortable to hold and use, they ALWAYS worked, and the sound was excellent, or at least very clear and understandable. Now of course a smart phone rides around in my pocket so I have a phone everywhere. But it's an ergonomic nightmare, has atrocious sound, frequently breaks up, and here in West Texas, stops working altogether at the drop of a hat. So, in some ways it's better, but in others a definite step down from the not-so-good-ol days. Great series. I'm really glad to have found it!
I was able to see a more modern version of this machine actually operating inside a working telephone exchange. The machine I saw was still mostly mechanical but was a more advanced version which occupied only about as much space as one of the electric motors in the machine shown in the video. Actually, less space, since it had a smaller diameter.
There were actually two machines, in case one failed or required maintenance, so the tones would continue without interruption.
The machine generated two basic tones. If I remember correctly, they were 25Hz and 600Hz. The 25Hz was used to provide the ring current for the ringer, the 600Hz was used to provide the busy tone and congestion tone and the two were mixed together in order to provide the characteristic dial tone and when interrupted, ring tone.
Of course this was in Australia where the tones are slightly different to the American tones.
The machine also provided all of the mixing and the appropriate interruptions.
Modern amplification methods meant that the machine didn't have to handle huge currents and so could be smaller than older machines.
No idea these ever existed - thanks Sarah
I've had one of those crimpers in the center top of the tool board floating around my tool collection since I was a kid and I finally know what it is.
Now here's some fresh anxieties to consider: accidentally dropping your ringing machine while moving it. Great 😂
I always find it interesting learning how technical features were implemented years ago. I had not thought about how the other telephone tones were produced. Contrast this rotary ring generator with the fiber ONT (optical network termination) I have for internet and to emulate legacy POTS. The ONT is about the size of a 3x5 index card and about 1/2 inch thick. Beside all the internet stuff it provides the Central Office BORSCHT (battery, overvoltage protection, ringing, signaling, coding, hybrid and test) functionality. As amazing as my little ONT is I doubt any will survive 100 years to live on in a museum.
I study OTR (old time radio) shows, and direct & perform in recreations of them.
One thing I've noticed in the original OTR shows is that the telephone tones and dialling pulses sound lower and more clicky than the modern tones of the 1970s onward.
To make my recreations sound more authentic, I use the old telephone sound effects.
Wonderful... more please. These videos are so informative thank you so much Sarah.
I loved the old ring back and other tones.
Hi Sarah,
At some point, would you please do a video about the various sounds generated from the time of the ring generator to current day, and what they meant - things like "reorder" throughout the years, and the (I'm not sure what they're actually called) 3-tone signals?
I've been watching these videos for quite a while, and at some point, I need to get off my butt and come take the tour.
Thanks for the work you put in to your videos, and keeping the working history of something we take for granted alive.
The 3-tone signal you’re talking about may be special information tone or SIT
@@gadgetboyj Yes, that's what I mean. What about them I can find online isn't very descriptive of what function they serve.
Slow busy was phone busy....Fast busy was equipment busy....
Good to see you again!
Great explanation. I learned so much!
HAMMOND B3! WOOOO! My favorite band had a B3 as a permanent part of the band. They also were the first rock band to use 2 drummers, which was picked up by their lead guitarist from James Brown.... Figured it out?
The Allman Brothers Band! 🙏👌🎸
This is so interesting ! Can't wait for the next video.
Came across this video due to a friend linking it but remember you from a video I saw years ago. glad to find you here and subscribe!
I loved the mercury switch; it reminds me of the tilt bulb ones I worked with in various devices but turning the idea around.
Hm, yeah it is kinda like those little mercury bulbs that were in old thermostats!
As a kid in the 70s, I am reminded of GE's Super Switch, a mercury bulb based light switch.
Love the video. Camerawork and the content was excellent. More and more please :)
420 reference ..i dig it ..i am surprised none of the tones are at 440 mhz like the guitar ..i gots to admire the boomer generation and older for their amazing engineering that built this country ..my question is ..where did all the billing take place ..was there a machine that did that ..idk ...great videos and well presented ya'all :)
Billing is quite a complex and interesting subject. I hope to do a series of videos on that someday.
excellent video ....Thank you for posting these
Thanks for the detailed explanation!
That was a fantastic video, keep up the good work !
I have a question about the changeover process of this from old to new. I grew up in Spanish Fork, Utah, and I specifically remember these wheel-tones being our ring-back and dial tones, and you or Evan told us somewhere that these almost always came with a crossbar 5, so I guess that that's what Spanish fork started with, maybe back in the '50s or '60s, with the prefix of 798 (with Utah's 801 area code). I only remember back to the mid/late 70s though. Our dial tone was sounding pretty crappy in the late 80s. Oddly enough, not only had it gotten fairly crackly, but I think I even remember the frequency having little bursts of slowing periodically. But I can't remember that for sure.
One day in October 1990, I picked up a phone and heard a NEW dial tone, and it was _clean,_ like a brand-new machine was making it! It sounded like the one that Provo and similarly bigger cities around had already been using since I was ever aware, like back in the 70s, and I was like, "HUH, now WE have this!" I dialed out and sure enough, it sounded just like ring-out did when I called somewhat bigger cities like Provo, Orem, or Salt Lake City! And then I wondered what the changeover was like!
So even now I wonder what it would have sounded like if I had picked up the phone overnight right while they were turning the old tone machine off, disconnecting it, and then turning the new one on. Do you think I would have just heard the last of the old tone, some clicks, blanking, more clicks, and then the new tone, because they plugged it over before turning the motor off, or do you think I would have heard the old tone wind down to a stop because they left it in circuit while they turned it off, and then some clicks, blank, clicks and the new tone immediately on because it's solid-state instead of rotary?
Great explanations of some pretty esoteric stuff. Thanks for another high quality video!
Thanks, glad you enjoyed it :)
Those interrupters are particularly clever little things aren't they, so simple in their design and yet rather effective at the task required. Certainly beats regularly burning out contacts if they were to have used cams or constantly polishing your ring as with the older systems. Thank you for another really interesting video Sarah, I'm already eager for the next installment! (P.S. Were you responsible for the graffiti?! 😄 )
I used to enjoy working in the power room (4000A -48VDC, ±130VDC, -24VDC, and IIRC there was a small converter for some sort of 36 volt use). Polished a whole lot of commutators and slip rings in my day. 😀
Sarah; thanks for another very informative video. The concept of 'city ring' gave me a laugh. Had not thought about it, but understand how that phase developed. I also remember the startling change to the call progress tones, with the cut over to ESS. How does the 20Hz ring output waveform, of this machine compare with the old hand crank magneto and electronic ring plant that replaced these rotating machines?
I wish I never passed up all that old telephone equipment the old telephone company tried to give me back in the 90s.