Teletype - test-drb@ccmp.vtda.org

2 Jun 2003

...
 From: ard(a)p850ug1.demon.co.uk

  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. 
Hi
 It is also possible that he has the wrong speed gears/motor.
A 60Hz motor will run in local with 50Hz connected but the
Baud rate to the outside will be wrong.
Dwight

...

 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 