[GreenKeys] Printer over the phone lines.

[Richard YOUL Brisbane]

To Jan Bogue,

This has been my specialty for some years, and although the number of
followers has been disappointing, the technology has been successful.

With some assistance I have devised interfaces to go between teleprinters
and modems, and these have been successfully used over phone lines for some
years. Connecting a printer directly to the phone socket is sure to cause
consternation at the phone exchange!

I have circuits for both single current (neutral I think you call it) and
double current (polar) teleprinters. With minor modifications they can be
used for either RE232 modems which work on    +12v (space) and -12v for a
mark. (Space is the equivalent of no current in the receive magnet
and mark is when the magnet is pulled shut). Another type of modem is called
TTL and it uses
+5v for a space and zero volts for a mark. This latter is the type of modem
I normally use.

The single current interface has 3 transistors, some resistors, diodes and
capacitors which you should find at Radio Shack type suppliers. If you are
just OK with a soldering iron, constructing one should be possible in a
couple of hours.

The other requirement obviously is that the other person uses the same modem
tones. For the 'old' 300 baud modems, there is the Bell standard and the
CCITT (world standard) tones and they are not interchangeable, but some
modems can be switched to whichever of the two is desired. I think the CCITT
standard is called V24.

You are obviously quite new to the wonderful world of teleprinters, and may
feel put off by sometimes conflicting advice on what can and can't be done.
I had no formal training with printers, but often not knowing what
(officially) would not work, I did it anyway and often it did work. While
loop voltages in excess of 100VDC are no doubt necessary for operation over
lines many miles long, I have found that the Teletype Model 15 works quite
well with a loop voltage as low as 30DC. The only disadvantage may be the
need to more carefully adjust the Rangefinder.

Anyway if nobody comes up with anything better, I would be happy to send
circuits etc as you may require. Your newness to teleprinters is about the
same as mine with E-Mail etc so for circuits etc it may be necessary to rely
on the old snail mail.

I did once work teleprinter to computer in New Zealand, but would be
interested in trying a connection to the USA.

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Somebody has devised a system whereby the Internet can be used for Morse
Code working even using Morse Keys and sounders. Has anybody succeeded in
doing the same for Teleprinters?