Electronic for ED1000 Interface

TODO

In frequency domain ...

When sending a character the transmitter switches between the corresponding frequencies with the given baud rate.

In the old days a lot of electronic components were required to build a modulator and demodulator for Frequency Shift Keying (FSK). Today most of the work is done by software.

For our project, we use a (USB) sound card to play and record the carrier frequencies, and just 5 electronic components adapt the audio signal to the teletype ED1000 specifications.

With this USB sound card adapter the teletype can be connected to a Windows-PC, a Linux-PC, a Mac (not tested) or a Raspberry Pi (not tested). For Raspberries, a USB sound card is needed and available in online shops for about 10€. With PC or Laptops, their built-in sound card is equally suitable.

Connecting a PC Sound Card to ADo8

ADo8 Plug

Pin	Description
1	Line a
2	nc
3	nc
4	Line b
5	Bridge to 6
6	Bridge to 5
7	nc / Option: Paper-End-Switch
8	nc / Option: Paper-End-Switch

The line wires are used to send and receive at the same time like a MODEM on phone wires.

The bridge between pin 5 and 6 is for signaling a connected plug. Caution: Some teletypes apply high voltages here!

Some teletypes use a switch (relay) on pin 7 and 8 to indicate "end of paper".