when we started our trace at final frame we put a spring clothes pin on the rod to keep that rod in place. we also took a paper ticket with us to write down the trace results. we could then take the ticket to the other office (if in the same CO) for the trace to be completed.
@@ds99 great question!!!! To be totally honest i have no idea!!! I was told to do it by a really senior switchman. After all the panel schools and looking back it makes no sense!!
In the early '80s I worked electronics in an air traffic control center. We had what we called a "bomb relay" on our main line. As long as we didn't hang up the call wouldn't be torn down which gave us time to trace it. Thanks Sarah! First time I've ever seen any sort of real, public explanation for how tracing works.
I guess my memory must be failing. As I recall. we could trace a call within about five minutes within our office. -- With four or five people. We had several high-priority numbers wired in advance to convert to "called party hold". That certainly gave us a little more time. This was a Stromburg-Carlson XY switch with 10000 lines. Someone would start at the Final Connector and simply yell out the path through the connectors to the next person. Called party hold meant that we could complete our trace after the calling party hung up.This was on a USAF Base, so a call arriving from a civilian (off-base) C.O. generally could not be traced because the civilian C.O. would not cooperate. Having recently retired as an AT&T tech, I now reflect back in awe at what was accomplished with an electro-mechanical system.
Excellent video. I did call traces in the SxS system in the 70's, usually nuisance calls. If a called subscriber had them frequently, we would insert "traps" in each connector t/r associated with that number. That would hold up the whole switch train as long as it is local in the exchange and the called subscriber didn't hang up the phone until we had it traced. Thank you so much. Quite interesting on a common control office.
I worked at "major" regional ISP circa 2000. Major meaning we had our own telecom switch in addition to a few thousand twisted pair lines. I thought the hardware was intimidating, but I mostly with worked with SS7 software interface (in terms of dial-up service). But it was nothing like facility in your video... a totally humongous mix of electrical and mechanical circuits. Thanks for blowing my mind!
Thanks for your work. When I was a teenager I loved hanging around telephone exchamges. They were step-by-step and were transitioning to crossbar. I've always been fascinated by them. Your in depth knowledge and detail are very impressive.
In the Oakland #4M Xbar office the incoming and outgoing frames were scattered over two buildings and two floors of each building and not in any logical order so it took a bit of luck and skill to trace a call. There were a couple of in-link frames that were hidden among frame of other types so you would never think to look back in the dark corner where they stuffed them. As long as the call was not on those 'hidden' frames or you had been tracing calls there for 15 years it usually was not too complicated but almost always involved a lot of walking and stair climbing but the new #4 office on the 15th floor was organized in an orderly fashion and it was so easy to trace a call there it felt like cheating to us old guys who had been in the old 4M office for decades. Tracing wires on the MDF was just as bad as the blocks were not in any particular order, they put them where there was space so there would be a whole bunch in order and suddenly they would end and woe unto you if you did not know where they went from there. 15 months as a Frameman provided the knowledge as to where everything was as we were always adding and removing circuits. They would add 10 circuits one month and the next month to some office and they would have us yank out 5 or 6 the next month and it went on like that for every long distance office, something to do with paying taxes on unused/underused circuits versus overload levels if there were not enough trunks. The "churn" in trunk provisioning gave us a lot of overtime keeping up with all that nonsense and we went through tons of copper wire.
Wow, I wonder how the 4M office got that way. I'd imagine that if they had total design freedom, they would have put everything together, all in the same space like they did for the 4A on the 15th floor. I guess because the 4M went in first, as it expanded they had to figure out how to put frames wherever they could fit them. Must have been a cabling nightmare though.
@@ConnectionsMuseum The #4 Xbar office was originally a 10x10 inlink/outlink frame office and upgraded to a 20x20 and then subsequently to a 40x40 frame and upgraded from a #4 Xbar to a #4M (Modified) to be functionally the same as a #4A. There was a VO/NVO modification in there somewhere too. The overseas gateway added some issues too. With all these upgraded done at different times and a new building was also added where much of the high end frames were installed it got scrambled up pretty good. That is the Nutshell explanation, it was a nightmare for anyone from a #4A but we never knew anything else so got used to the bastardized layout. The wimps who came in and ran the office after I was gone from there made up a book with all the locations in it so they could look them up. Not so with the old guys it was a right of passage to learn the layout. Instead of learning the ropes like a sailor we had to learn the frames and MDF layout.
My dad worked in a toll regional center in the 60's and 70's, so I'm very familiar with the 4A switching, (it took up 2 whole floors) I'd heard of 4M but I didn't know anything about it. Thank you for the information! I miss those days. When they shut down the 4A, I cried! This was the San Bernardino, CA toll office. I heard they sent the entire 4A crossbar switch to Mexico!
Back in about 1965-66, I was about 11, and had an old wall phone given to me by a relative. It had been sprayed some awful colors pin k and purple metal flake. I cannibalized it for the dial and proceeded to hook the dial and an intercom up to the phone lines in the basement. A friend and I made lots of crank calls with that lash up. A few days later I was on the front steps reading a comic when the phone truck pulled up and a lineman got out with his linemans belt and butt set. He asked if my parents were home, thankfully no, and if this was the house that was getting all the wrong numbers! He left and never came back! I imagine a lot of time was spent tracing our line there in Trenton.
Did a lot of traces in a SxS office on night shift for Suicide Prevention Bureau in Los Angeles. Most originated in other offices. If they originated in my C.O. we would have to go upstairs to the Plant Service Center pull the subscriber line card and call that information to the Chief Special Agent who would relay that information to law enforcement. Many times the call would drop before the trace was completed.
It starts with Fender! A Jazz Bass, a TR, plus some Messy Booger... nice :) Love your insights. I may not be too much of a movie afficionado, but being a tech nerd, it's all so fascinating. You're still a friggin' genius to remember all the details of how you wired the stuff. I can't do that on my designs, or code... that's why if I don't draw a schematic, I'll have to reverse-engineer my own invention later on. Takes more time than doing proper documentation, so I just write it down and draw it, for the future Keri's mental health's sake, haha!
One of the documentaries I watched involved a call trace and each US office had done the trace quickly and reported they'd tracked it to the next one over. When they traced it over seas into west Germany, the office there said they needed more time since they were running older equipment and the call was dropping too quickly for them to trace it. Thank you for giving context to why they had to hold the call for a few hours so the office in German could complete the trace.
It's good to hear that occasionally "Hollywood gets it right" and the scene from "The Slender Thread" is fairly accurate. It would be nice if Sarah could analyze the scene in more detail, describe the equipment that they were using and going through each part and discuss what was realistic or not. Would it really take "half the movie" - perhaps one hour just to complete one trace?
Hang on for the next video, out tomorrow. I don’t explain the scene in detail but I do trace a call through the same type of switch (in the same room that the movie was shot in), and talk about it a little more.
Guess this is a question for the group, but would having a photo/polaroid taken of each frame help with identification after the call has ended? Also, is there a button and associated light you can hit to indicate that THE CALL IS ORIGINATING IN THE BUILDING!!!
Kudos. I started to watch a lot of your videos one month ago and this was one of my questions. It is much easier now with ss7, and we have new problems with SIP.
awesome. would be more fun to have a volunteer setup the call and have you trace it and find it. harder level is have 2-3 calls static on in total while the sim is running the other rods. more of a challenge to find the caller of the target phone.
@@t13fox67 not familiar with cama, I would guess Crossbar AMA? As things were converting to magnetic, the SXS was being decommissioned, as was the 5-crossbar... and I ended up in an SCC at that point... and on to more modern(at the time) switches.
@@t13fox67 late 70's (no idea what class of sxs, but 30k+ main stations next to a 2.5 prefix crossbar, and a 1A ESS which I had no part of.. 80's went to a bunch of other switches, mostly SCC oriented. Stromberg Carlson, DMS10,100/200/5ESS and.. then the fiber terminals and dslams etc... Also worked on the SCCS 3b5/15's Datakit 2k, lots of different stuff.
This is so cool i grew up in a telephone office. My Dad was on the ground floor of the microwave progrsm. I can remember being taught anout all the tools in the frame, switching and crossbar. He moved onto toll and microwave when i was 13 years old. The Slidell,LA office was half way between Clear Lake Tx snd and Cape Kennedy and the NASA computer center was located in Slidell. My Dad was with the Bell System for 50 years before ge retired.
I would have thought (since this is metallic switching without filtering), you could apply an “out of band” tone or DC bias that could be traced with a detector wand?
Out of band tone *could* work, but a DC bias would not. There are repeat coils (transformers) on the incoming and district circuits, so there is no full metallic path from the calling to called subscriber.
Serra you're so cool. If "the call was coming from inside the house" (like in the old trope) what would the call tracing look like then? Would it be easier or harder? Would you have to trace a big loop back to the beginning, or would it be more trivial? Thanks for the video!
I got to see inside of a At&T rotary switch building in the 80's. It was interesting to see all those rotary switches operate when someone made a call and they also had large lead acid batteries for power back up.
Nowadays with some many SIP/VOIP providers out there, those "scam" calls from India pretending to be the IRS or Social Security are next to impossible to trace!
IRS AND SOCIAL SECURITY seldom use foreign off premise employees especially foreign sounding. You can usually curse them off and hang up. If someone shows up at your door step, let them know you thought it was an Indian scammer, not my problem. BTW, spoofing a phone number not belonging to you to scam an individual in the USA is a federal offense, contrary to popular myths systems in the USA can electronically trace calls in an investigation. IP calls are traceable within the states.
Always wanted to know about this. Had some co-workers who worked for the phone company said never had any experience with tracing calls likely their jobs were in the field fixing phone wiring.
It took a lot of running around, climbing ladders and counting two motion selector switch positions to call trace on a Strowger exchange. It took several minutes.
I vividly remember watching (I think The Rockford Files or Hawaii 5 0 *the original*) and them catching a person in the act of doing a drug deal or something at a payphone and they needed to hold the call up and they showed taking the transmitter out and holding the phone off hook and a person tracing in a step office. I could only assume that they were trying to make sure that the line was silent.
I cannot unsee the uncanny resemblance of her glasses and the Belgian flag. 🇧🇪 Is that on purpose, a coincidence or am I imagining things? 🤔 Oh, and excellent video! I finally get how that worked, I'll watch part two right away.
omg in what world did i just entered 😮. I watched the hole thing this is fascinating how the world was before computers. It makes me think that stuff like this was engineered by some brilliant people and nowadays all that knowledge is being lost. I wish i could talk to people that developed and operated those and they would probably have like best practices on what some minor thing was back then, just like we have like patterns and standards to develop software
Another film reference for a call trace scene, in this case on a Step-by-Step switch: "Black Christmas" (1974). ua-cam.com/video/tbK2GfN-E18/v-deo.html
In the 80's my dad was getting threats on our home phone and had to work with the police and Mountain Bell to trace the call. I remember him having to hold the line open for a minute, write down the time and then call a specific number to give them info. I don't know if it was PD or Telco he called.
If the bad boy caller was Oliver Douglas several states away using a switch at the Hooterville Telephone Company, would you ever be able to figure that out before he hung up?
Depends on the type of switch I suppose. I know TDM switches work by reading a frame from each line into a memory buffer, then writing them out in a different order. This gets to go by the cool name of something like "spacetime fabric switch".
Flashlight 5:13 I love the high light output LED Torch, but the Chinese use such crappy push button switches that they all fail after a short time. I'm tempted to go back to my BrightStar D-battery industrial flashlight. Serra, where did you get that wonderful light is that type used by the Bell System?
@@ConnectionsMuseum my search found reference to it on line too. "IDd Bond First Electric Flashlight for Bell System" yours is still going strong after 103 years, my LED FL last about 3-months if I'm lucky.
@@mackfisher4487 China can make decent things, if you pay them enough. The cheap nasty ones you can get for a dollar are indeed awful, but I managed to get a decent one powered by a lithium cell for $15, and it's lasted for 3 years so far.
@@user2C47having worked for a company that provided video security systems we received a call from a Chinese supplier of cctv cameras trying to sell their products. We asked 'how much?' They replied 'how many years do you want it to last?" Well long story short cost determined longevity of their products. Now this would not have been bad had we known how cctv systems have evolved to IP systems. Get them through the hump and update them to more sophisticated systems.
That is quite a process and then as you mentioned if they hang up everything is lost. Yikes! That means hurry and don’t get stressed! You mentioned the switches were tripped. Were they tripped because a trace was in progress or do they always trip when connected?
Tripped because connected. You can see each selector has about 5 different brushes on it at different height levels. One of those is the correct height level and gets connected and the other ones are wrong connections that don't get connected.
I'm curious as to why there wasn't some some of punched tape or ticker tape which logged each successful connection documenting the frames involved in the CO. There would be a tape to cover each NNxx terminal number so there would be a tape for each NN hundreds group. Then you could see that on tape 56 has something like "5678-322-29.3-11.5". (terminal#-incoming trunk#-incoming frame#.brush#-final frame#.brush#" So then you could just look for the last log for 5678 and find the active incoming trunk (322) on incoming frame 29 brush 3 to final frame 11 brush 5". Or something like that.
Assuming there are 30,000 terminals in an average size office, thats 30,000 extra wires you have to run to to record when a terminal is accessed. Also, each selector rod does not "know" which previous selector or terminal has seized it, so you'd need a system of storing that information...a "memory" for each selector and each path in the office that would be accessed. Then frames of control equipment to print a tape, for tens of thousands of calls per day. Memory was not easy to engineer in the 1920s, and would have probably taken months or years to figure out how to do all of that. That would not be a reasonable use of resources.
@@ConnectionsMuseum Gotcha. I see the problem now. I forgot that once the CO is reached on a trunk the last remaining digits are still unknown and are awaiting reception to then route inside the CO to the correct terminal block. 1ESS must have seemed like magic.
@@ConnectionsMuseum When I was a kid in the 1950s I was hanging around the local (usually unmanned) CO when someone showed up, and I got him to give me a tour. I remember that there was a case full of paper tape punches on the end of one of the rack rows, with maybe 20 or so tapes, and every so often one of them would punch out a bunch of numbers. The guy explained that this was for billing. It recorded the calling and called numbers and the call duration. He said that one a month the tapes got taken elsewhere and processed to make the customer bill. I do remember that phone bills in those days did show the called number and duration, which no longer show up on phone bills. So they must have had some way of recording that information. Of course this was a little CO with Stroger switches and probably around 8K lines max, probably a lot less than that.
@@lwilton Yes, that sometimes call bill tracing or origins tracing. It was very rarely used as it required waiting until the end of the billing period and monitoring all outgoing bills (nationwide!) for the called number. That's slow and an incredible amount of work. Where it works very well is when you have a list of suspected originators and want some evidence for a trial...
I am curious about the phone that made the call. I used to see them a lot in offices with the mechanical push buttons and once saw a relay panel they connected to but have no idea how it works. I have only dealt with digital pbxs. What kind of system is it? I would like to research it.
The phone is a “Call Director” and it is wired in to the museum 1A2 key system. telephonecollectors.info will have some places to start if you search for those terms.
@@ConnectionsMuseum Cool. I used to see them everywhere. Big clunky light up buttons and centronics connectors to 20? pair but have no idea how they work. Now down the rabbit hole.
when we started our trace at final frame we put a spring clothes pin on the rod to keep that rod in place. we also took a paper ticket with us to write down the trace results. we could then take the ticket to the other office (if in the same CO) for the trace to be completed.
What does keeping the rod in place do? Does it tie up the lines so they cannot disconnect?
@@ds99 great question!!!! To be totally honest i have no idea!!! I was told to do it by a really senior switchman. After all the panel schools and looking back it makes no sense!!
Maybe as a backup for the paper. Or to be able to take a photograph as evidence for court 🤔@@roylamkin7177
In the early '80s I worked electronics in an air traffic control center. We had what we called a "bomb relay" on our main line. As long as we didn't hang up the call wouldn't be torn down which gave us time to trace it.
Thanks Sarah! First time I've ever seen any sort of real, public explanation for how tracing works.
I guess my memory must be failing. As I recall. we could trace a call within about five minutes within our office. -- With four or five people. We had several high-priority numbers wired in advance to convert to "called party hold". That certainly gave us a little more time. This was a Stromburg-Carlson XY switch with 10000 lines. Someone would start at the Final Connector and simply yell out the path through the connectors to the next person. Called party hold meant that we could complete our trace after the calling party hung up.This was on a USAF Base, so a call arriving from a civilian (off-base) C.O. generally could not be traced because the civilian C.O. would not cooperate.
Having recently retired as an AT&T tech, I now reflect back in awe at what was accomplished with an electro-mechanical system.
Excellent video. I did call traces in the SxS system in the 70's, usually nuisance calls. If a called subscriber had them frequently, we would insert "traps" in each connector t/r associated with that number. That would hold up the whole switch train as long as it is local in the exchange and the called subscriber didn't hang up the phone until we had it traced. Thank you so much. Quite interesting on a common control office.
I love this channel! I didn't know one person set this up! Thank you! I'm 70 and retired ham and electronics hobbyist but this beats all!
I worked at "major" regional ISP circa 2000. Major meaning we had our own telecom switch in addition to a few thousand twisted pair lines. I thought the hardware was intimidating, but I mostly with worked with SS7 software interface (in terms of dial-up service). But it was nothing like facility in your video... a totally humongous mix of electrical and mechanical circuits. Thanks for blowing my mind!
Thanks for your work. When I was a teenager I loved hanging around telephone exchamges.
They were step-by-step and were transitioning to crossbar. I've always been fascinated by them.
Your in depth knowledge and detail are very impressive.
In the Oakland #4M Xbar office the incoming and outgoing frames were scattered over two buildings and two floors of each building and not in any logical order so it took a bit of luck and skill to trace a call. There were a couple of in-link frames that were hidden among frame of other types so you would never think to look back in the dark corner where they stuffed them. As long as the call was not on those 'hidden' frames or you had been tracing calls there for 15 years it usually was not too complicated but almost always involved a lot of walking and stair climbing but the new #4 office on the 15th floor was organized in an orderly fashion and it was so easy to trace a call there it felt like cheating to us old guys who had been in the old 4M office for decades. Tracing wires on the MDF was just as bad as the blocks were not in any particular order, they put them where there was space so there would be a whole bunch in order and suddenly they would end and woe unto you if you did not know where they went from there. 15 months as a Frameman provided the knowledge as to where everything was as we were always adding and removing circuits. They would add 10 circuits one month and the next month to some office and they would have us yank out 5 or 6 the next month and it went on like that for every long distance office, something to do with paying taxes on unused/underused circuits versus overload levels if there were not enough trunks. The "churn" in trunk provisioning gave us a lot of overtime keeping up with all that nonsense and we went through tons of copper wire.
Wow, I wonder how the 4M office got that way. I'd imagine that if they had total design freedom, they would have put everything together, all in the same space like they did for the 4A on the 15th floor.
I guess because the 4M went in first, as it expanded they had to figure out how to put frames wherever they could fit them. Must have been a cabling nightmare though.
@@ConnectionsMuseum The
#4 Xbar office was originally a 10x10 inlink/outlink frame office and upgraded to a 20x20 and then subsequently to a 40x40 frame and upgraded from a #4 Xbar to a #4M (Modified) to be functionally the same as a #4A. There was a VO/NVO modification in there somewhere too. The overseas gateway added some issues too. With all these upgraded done at different times and a new building was also added where much of the high end frames were installed it got scrambled up pretty good. That is the Nutshell explanation, it was a nightmare for anyone from a #4A but we never knew anything else so got used to the bastardized layout. The wimps who came in and ran the office after I was gone from there made up a book with all the locations in it so they could look them up. Not so with the old guys it was a right of passage to learn the layout. Instead of learning the ropes like a sailor we had to learn the frames and MDF layout.
@@JohnBare747 wow....
@@mihailmilev9909 Now seems like it was Long, long ago in a universe far, far away
My dad worked in a toll regional center in the 60's and 70's, so I'm very familiar with the 4A switching, (it took up 2 whole floors) I'd heard of 4M but I didn't know anything about it. Thank you for the information! I miss those days. When they shut down the 4A, I cried! This was the San Bernardino, CA toll office. I heard they sent the entire 4A crossbar switch to Mexico!
You are a great teacher, I enjoy all of your videos!
Back in about 1965-66, I was about 11, and had an old wall phone given to me by a relative. It had been sprayed some awful colors pin k and purple metal flake. I cannibalized it for the dial and proceeded to hook the dial and an intercom up to the phone lines in the basement. A friend and I made lots of crank calls with that lash up. A few days later I was on the front steps reading a comic when the phone truck pulled up and a lineman got out with his linemans belt and butt set. He asked if my parents were home, thankfully no, and if this was the house that was getting all the wrong numbers! He left and never came back! I imagine a lot of time was spent tracing our line there in Trenton.
Did a lot of traces in a SxS office on night shift for Suicide Prevention Bureau in Los Angeles. Most originated in other offices. If they originated in my C.O. we would have to go upstairs
to the Plant Service Center pull the subscriber line card and call that information to the Chief Special Agent who would relay that information to law enforcement. Many times the call would drop before the trace was completed.
Love the use of a period light
It starts with Fender! A Jazz Bass, a TR, plus some Messy Booger... nice :)
Love your insights. I may not be too much of a movie afficionado, but being a tech nerd, it's all so fascinating.
You're still a friggin' genius to remember all the details of how you wired the stuff. I can't do that on my designs, or code... that's why if I don't draw a schematic, I'll have to reverse-engineer my own invention later on. Takes more time than doing proper documentation, so I just write it down and draw it, for the future Keri's mental health's sake, haha!
One of the documentaries I watched involved a call trace and each US office had done the trace quickly and reported they'd tracked it to the next one over. When they traced it over seas into west Germany, the office there said they needed more time since they were running older equipment and the call was dropping too quickly for them to trace it.
Thank you for giving context to why they had to hold the call for a few hours so the office in German could complete the trace.
Cuckoo’s Egg?
@@etc_kula Yeap, Nova did it back in the mid 90s.
One of these days I will make my way out there to see the museum. I could spend hours just watching the workings of these switches.
You're alive! YAY! We've missed you!
10:16 and the call was coming from **violin screech** INSIDE THE OFFICE
Imagine doing that in a panel office in midtown Manhattan at about 3PM. (in the old days)
Good job taking the viewers through the process. Thanks.
It's good to hear that occasionally "Hollywood gets it right" and the scene from "The Slender Thread" is fairly accurate. It would be nice if Sarah could analyze the scene in more detail, describe the equipment that they were using and going through each part and discuss what was realistic or not. Would it really take "half the movie" - perhaps one hour just to complete one trace?
Hang on for the next video, out tomorrow. I don’t explain the scene in detail but I do trace a call through the same type of switch (in the same room that the movie was shot in), and talk about it a little more.
Guess this is a question for the group, but would having a photo/polaroid taken of each frame help with identification after the call has ended? Also, is there a button and associated light you can hit to indicate that THE CALL IS ORIGINATING IN THE BUILDING!!!
Kudos. I started to watch a lot of your videos one month ago and this was one of my questions. It is much easier now with ss7, and we have new problems with SIP.
Hopefully STIR/SHAKEN will help with some of the issues plaguing SIP. But we are still years away from a complete solution.
Also a good tracing scene, as well as other phone related stuff in: Three Days of the Condor (1975)
Three Days of the Condor pretended that the tracing was automated. It is not, presumably until ESS.
Completely unrealistic tracing scene
awesome. would be more fun to have a volunteer setup the call and have you trace it and find it. harder level is have 2-3 calls static on in total while the sim is running the other rods. more of a challenge to find the caller of the target phone.
Your videos bring back some old, and really fun memories. :)
Can't hardly wait to see call tracing part 2 on the no.5.
It would be really interesting to revisit this one on the DMS-10.
@@benjaminchung991 I’ll ask Matt to do a video on it :)
It’d also be interesting to see the same process on a 1ESS.
32 years in telecom, first time I have seen a panel office, although I have worked a bit with line bays used in a SXS/SAMA.
I work SxS with cama and tracing calls thru cama was indeed interesting..ted.
@@t13fox67 not familiar with cama, I would guess Crossbar AMA? As things were converting to magnetic, the SXS was being decommissioned, as was the 5-crossbar... and I ended up in an SCC at that point... and on to more modern(at the time) switches.
@@PrimRoseLane CENTRALIZED AMA or cama. I worked class 4 and 5 SxS with cama during the 70's at eldon mo.
@@t13fox67 late 70's (no idea what class of sxs, but 30k+ main stations next to a 2.5 prefix crossbar, and a 1A ESS which I had no part of.. 80's went to a bunch of other switches, mostly SCC oriented. Stromberg Carlson, DMS10,100/200/5ESS and.. then the fiber terminals and dslams etc... Also worked on the SCCS 3b5/15's Datakit 2k, lots of different stuff.
@@t13fox67 perf paper tape billing was a lot of interesting. keeping perforators clean was quite a challenge.
This is so cool i grew up in a telephone office. My Dad was on the ground floor of the microwave progrsm. I can remember being taught anout all the tools in the frame, switching and crossbar. He moved onto toll and microwave when i was 13 years old. The Slidell,LA office was half way between Clear Lake Tx snd and Cape Kennedy and the NASA computer center was located in Slidell. My Dad was with the Bell System for 50 years before ge retired.
Woohoo! Fellow bass player! Immediate reaction, haha. Now for the rest of the video!
It's very cool this was even possible to do back then.
I would have thought (since this is metallic switching without filtering), you could apply an “out of band” tone or DC bias that could be traced with a detector wand?
Out of band tone *could* work, but a DC bias would not. There are repeat coils (transformers) on the incoming and district circuits, so there is no full metallic path from the calling to called subscriber.
Serra you're so cool. If "the call was coming from inside the house" (like in the old trope) what would the call tracing look like then? Would it be easier or harder? Would you have to trace a big loop back to the beginning, or would it be more trivial? Thanks for the video!
We traced the call, it's coming from inside the office. You hear me? It's coming from inside the office. You need to get out of there right now!
Not now, can't you see I'm on the phone?
I got to see inside of a At&T rotary switch building in the 80's. It was interesting to see all those rotary switches operate when someone made a call and they also had large lead acid batteries for power back up.
Nowadays with some many SIP/VOIP providers out there, those "scam" calls from India pretending to be the IRS or Social Security are next to impossible to trace!
IRS AND SOCIAL SECURITY seldom use foreign off premise employees especially foreign sounding. You can usually curse them off and hang up. If someone shows up at your door step, let them know you thought it was an Indian scammer, not my problem. BTW, spoofing a phone number not belonging to you to scam an individual in the USA is a federal offense, contrary to popular myths systems in the USA can electronically trace calls in an investigation. IP calls are traceable within the states.
Ah yes, a fellow phone phreak from back in the days lol oh how I miss the good ol days
Always wanted to know about this. Had some co-workers who worked for the phone company said never had any experience with tracing calls likely their jobs were in the field fixing phone wiring.
It took a lot of running around, climbing ladders and counting two motion selector switch positions to call trace on a Strowger exchange. It took several minutes.
"It's coming from inside the building!!"
Highly recommend Black Christmas! It has a highly detailed sequence in which they trace a call like this.
I vividly remember watching (I think The Rockford Files or Hawaii 5 0 *the original*) and them catching a person in the act of doing a drug deal or something at a payphone and they needed to hold the call up and they showed taking the transmitter out and holding the phone off hook and a person tracing in a step office. I could only assume that they were trying to make sure that the line was silent.
If the call went through 2 class 5 offices and a class 4 office, it still took some time. Maybe with CCS7, it reduced the time it took.
Good stuff. Thanks.
Here's to things smoothing out in your life.
I cannot unsee the uncanny resemblance of her glasses and the Belgian flag. 🇧🇪
Is that on purpose, a coincidence or am I imagining things? 🤔
Oh, and excellent video! I finally get how that worked, I'll watch part two right away.
I'm always happy to see you on a new video :)
omg in what world did i just entered 😮. I watched the hole thing this is fascinating how the world was before computers. It makes me think that stuff like this was engineered by some brilliant people and nowadays all that knowledge is being lost. I wish i could talk to people that developed and operated those and they would probably have like best practices on what some minor thing was back then, just like we have like patterns and standards to develop software
@@MichaelWallace-oq3wd 👍🇵🇱 -tnx.
Excellent! Thank you for all that you do.
Could you ground out the sleeve lead on the last frame (or something like that) to hold the switching setup in place to trace a call?
Another film reference for a call trace scene, in this case on a Step-by-Step switch: "Black Christmas" (1974). ua-cam.com/video/tbK2GfN-E18/v-deo.html
In the 80's my dad was getting threats on our home phone and had to work with the police and Mountain Bell to trace the call. I remember him having to hold the line open for a minute, write down the time and then call a specific number to give them info. I don't know if it was PD or Telco he called.
If the bad boy caller was Oliver Douglas several states away using a switch at the Hooterville Telephone Company, would you ever be able to figure that out before he hung up?
Haha!
There's an interesting insight into international call tracing in the book The Cuckoo's Egg
i know because i wired it ..i started giggleing ..lol..
Beats MY hobby efforts!
Ok wow... I always assumed that there was some sort of record and that the "keep them talking" business was just a bit of dramatic license.
Cheers Sarah, that's a nice birthday present!
How did you know? 😀
@3:00 is that a hammock in the background? Is some sleeping in the office?
Is the scene in the movie, 3 days of the Condor any more or less accurate?
You must be a fellow hammocker. I spotted that too.
3 Days not accurate.
Great video! Looking forward to part two :3 I assume this would be much easier on the #3 and other ESSes?
Definitely! Those machines have a stored program and memory, so you just "ask" them.
In current networking switches (ethernet, infiniband, etc) the chip that does the "routing" is still called a crossbar. Or sometimes a crosspoint.
Depends on the type of switch I suppose. I know TDM switches work by reading a frame from each line into a memory buffer, then writing them out in a different order. This gets to go by the cool name of something like "spacetime fabric switch".
@@thewhitefalcon8539 I gave ethernet and infiniband as examples of the class I'm referring to
@@tolkienfan1972 I'm sure there are low-end ethernet switches that work the same way. (Not infiniband. If you're using infiniband it's high-end)
@@thewhitefalcon8539 100GbE nonblocking with latency measured in picoseconds. These aren't found in Microcenter.
@@tolkienfan1972 ok but not all switches are 100GbE rack-mount switches
Flashlight 5:13 I love the high light output LED Torch, but the Chinese use such crappy push button switches that they all fail after a short time. I'm tempted to go back to my BrightStar D-battery industrial flashlight.
Serra, where did you get that wonderful light is that type used by the Bell System?
Yes, it is! That flashlight was manufactured for the Bell System circa the 1920s.
@@ConnectionsMuseum my search found reference to it on line too.
"IDd Bond First Electric Flashlight for Bell System" yours is still going strong after 103 years, my LED FL last about 3-months if I'm lucky.
@@mackfisher4487 China can make decent things, if you pay them enough. The cheap nasty ones you can get for a dollar are indeed awful, but I managed to get a decent one powered by a lithium cell for $15, and it's lasted for 3 years so far.
@@user2C47having worked for a company that provided video security systems we received a call from a Chinese supplier of cctv cameras trying to sell their products. We asked 'how much?' They replied 'how many years do you want it to last?" Well long story short cost determined longevity of their products. Now this would not have been bad had we known how cctv systems have evolved to IP systems. Get them through the hump and update them to more sophisticated systems.
That is quite a process and then as you mentioned if they hang up everything is lost. Yikes! That means hurry and don’t get stressed! You mentioned the switches were tripped. Were they tripped because a trace was in progress or do they always trip when connected?
Tripped because connected. You can see each selector has about 5 different brushes on it at different height levels. One of those is the correct height level and gets connected and the other ones are wrong connections that don't get connected.
I'm curious as to why there wasn't some some of punched tape or ticker tape which logged each successful connection documenting the frames involved in the CO. There would be a tape to cover each NNxx terminal number so there would be a tape for each NN hundreds group. Then you could see that on tape 56 has something like "5678-322-29.3-11.5". (terminal#-incoming trunk#-incoming frame#.brush#-final frame#.brush#"
So then you could just look for the last log for 5678 and find the active incoming trunk (322) on incoming frame 29 brush 3 to final frame 11 brush 5".
Or something like that.
Assuming there are 30,000 terminals in an average size office, thats 30,000 extra wires you have to run to to record when a terminal is accessed. Also, each selector rod does not "know" which previous selector or terminal has seized it, so you'd need a system of storing that information...a "memory" for each selector and each path in the office that would be accessed. Then frames of control equipment to print a tape, for tens of thousands of calls per day. Memory was not easy to engineer in the 1920s, and would have probably taken months or years to figure out how to do all of that.
That would not be a reasonable use of resources.
@@ConnectionsMuseum Gotcha. I see the problem now. I forgot that once the CO is reached on a trunk the last remaining digits are still unknown and are awaiting reception to then route inside the CO to the correct terminal block.
1ESS must have seemed like magic.
@@ConnectionsMuseum When I was a kid in the 1950s I was hanging around the local (usually unmanned) CO when someone showed up, and I got him to give me a tour. I remember that there was a case full of paper tape punches on the end of one of the rack rows, with maybe 20 or so tapes, and every so often one of them would punch out a bunch of numbers. The guy explained that this was for billing. It recorded the calling and called numbers and the call duration. He said that one a month the tapes got taken elsewhere and processed to make the customer bill.
I do remember that phone bills in those days did show the called number and duration, which no longer show up on phone bills. So they must have had some way of recording that information. Of course this was a little CO with Stroger switches and probably around 8K lines max, probably a lot less than that.
@@lwilton Yes, that sometimes call bill tracing or origins tracing. It was very rarely used as it required waiting until the end of the billing period and monitoring all outgoing bills (nationwide!) for the called number. That's slow and an incredible amount of work. Where it works very well is when you have a list of suspected originators and want some evidence for a trial...
How does call tracing work on an ESS?
Great info! Thanks!
Fantastic thanks for posting!!
Is it easier if you know ahead of time that you want to trace every call to and from a specific number? Or is the process just as time consuming?
Great video!
I am curious about the phone that made the call. I used to see them a lot in offices with the mechanical push buttons and once saw a relay panel they connected to but have no idea how it works. I have only dealt with digital pbxs. What kind of system is it? I would like to research it.
The phone is a “Call Director” and it is wired in to the museum 1A2 key system. telephonecollectors.info will have some places to start if you search for those terms.
@@ConnectionsMuseum Cool. I used to see them everywhere. Big clunky light up buttons and centronics connectors to 20? pair but have no idea how they work. Now down the rabbit hole.
remarkable
Cool
You're soo number nine
Tracy
So all the movies where they traced a call are bullshit lol thanks