Your site should be Unesco'd as a world telecommunications heritage site. :) Really nice video explaining how the "fuzzy" mode pixel transmission is made.
As the original description for this clip states, you are looking at the mechanical font-memory of a Hell Feldfernschreiber teleprinter. This concept was invented and patented by Rudolf Hell in Germany in 1929. He actually invented digital character font, in particular he invented bitmap fonts. One of his bitmap font character sets comprised a 14x7 pixel bitmap (7 columns of 14 pixels). Before the 1970s, there were no solid-state font (character generator) ROM ICs, only mechanical. Rudolph Hell decided to capture the 14x7=98 pixels of each character of the keyboard as notches on a ring. I.e., one ring for each character, and open/closed switch contact for each ring. The keyboard is used to select the desired character = contact ring. The notched rings are stacked on a single shaft - the character drum. In the 1935/45 portable military Hellschreiber, the character drum (shown in the video clip) is not implemented a stack of notched disks. It is a smooth drum, made of an insulating material. Instead of notches, the surface of each ring has conductive metal patches. Again, each ring has its own slip contact. The video clip starts by showing the drum spinning a full speed, then slows down, and then shows an individual pixel-ring "track".
??????? I hope you were able to identify the spinning drum in the video clip. I also hope you were able to identify the shiny metal patches on the dark surface of the spinning drum. They represent pixels. As stated, these patches are arranged as rings. To transmit a character, you select a ring with the keyboard. This engages the slip contact that is associated with that ring, at the starting point of that ring. The pixel sequence of the selected character is then transmitted as a sequence of tone or current pulses to a Hell-printer. As you are having trouble comprehending this concept, I suggest reading the "how it works" and the "fonts" page of the referenced website (i.e., the pages www.nonstopsystems.com/radio/hellschreiber-function-operation.htm and www.nonstopsystems.com/radio/hellschreiber-fonts.htm respectively) where this is all explained and illustrated with much more detail.
JN03QO What exactly is represented on that drum? Am I supposed to be seeing alpha numeric characters on that drum or am I just supposed to be seeing binary or Morse code dots and dashes? All I see on that drum is random shapes.
Your site should be Unesco'd as a world telecommunications heritage site. :) Really nice video explaining how the "fuzzy" mode pixel transmission is made.
What am I supposed to be seeing on the drum? I can't make anything out? 73
As the original description for this clip states, you are looking at the mechanical font-memory of a Hell Feldfernschreiber teleprinter. This concept was invented and patented by Rudolf Hell in Germany in 1929. He actually invented digital character font, in particular he invented bitmap fonts. One of his bitmap font character sets comprised a 14x7 pixel bitmap (7 columns of 14 pixels). Before the 1970s, there were no solid-state font (character generator) ROM ICs, only mechanical. Rudolph Hell decided to capture the 14x7=98 pixels of each character of the keyboard as notches on a ring. I.e., one ring for each character, and open/closed switch contact for each ring. The keyboard is used to select the desired character = contact ring. The notched rings are stacked on a single shaft - the character drum. In the 1935/45 portable military Hellschreiber, the character drum (shown in the video clip) is not implemented a stack of notched disks. It is a smooth drum, made of an insulating material. Instead of notches, the surface of each ring has conductive metal patches. Again, each ring has its own slip contact. The video clip starts by showing the drum spinning a full speed, then slows down, and then shows an individual pixel-ring "track".
JN03QO
Yes but, what exactly am I looking at? What am I supposed to be seeing on that drum? I can't see anything depicted.
??????? I hope you were able to identify the spinning drum in the video clip. I also hope you were able to identify the shiny metal patches on the dark surface of the spinning drum. They represent pixels. As stated, these patches are arranged as rings. To transmit a character, you select a ring with the keyboard. This engages the slip contact that is associated with that ring, at the starting point of that ring. The pixel sequence of the selected character is then transmitted as a sequence of tone or current pulses to a Hell-printer. As you are having trouble comprehending this concept, I suggest reading the "how it works" and the "fonts" page of the referenced website (i.e., the pages www.nonstopsystems.com/radio/hellschreiber-function-operation.htm and www.nonstopsystems.com/radio/hellschreiber-fonts.htm respectively) where this is all explained and illustrated with much more detail.
JN03QO
What exactly is represented on that drum? Am I supposed to be seeing alpha numeric characters on that drum or am I just supposed to be seeing binary or Morse code dots and dashes? All I see on that drum is random shapes.
JN03QO
Right, so am I right in thinking, what I am seeing on that drum is Baudot code?