Teletype

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Mon Jun 2 16:19:00 2003

> Whenever I type anything I just get a left-arrow. I am blaming the
> 1818-23/-21 for this. Shouldn't I?

Maybe. Does the Model 33 work correctly when switched to 'local'? If not,
then you certainly have problems in the Teletype. If it does work in
'local' mode, then you might still have problems in the Teletype, but
problems with the interface are also possible.

>
> OK; current loop.
>
> Would this explain a resistor (14 Ohm, big) in the slot of the KSR would

Are you sure it's 14 ohms? I remember a multi-tapped power resistor with one
tap being about 1400 ohms in the standard current loop electronics for
the Model 33.

> get extremely hot when off this loop? Also; Hans Pufal, I would be most

And I think it does run hot. When switched to local, the teletype is
_still_ a current loop device, but the transmitter (keyboard contacts),
receiver (the selector magnet driver -- the little module with 2
transsitors in the Teletype electronics chassis) and a 'local' power
supply (which includes that resistor) are all in series. A current loop,
but one entirely inside the Teletype Model 33.

-tony
Received on Mon Jun 02 2003 - 16:19:00 BST