[GreenKeys] ASR33 modem

[Nico de Jong]

----- Original Message ----- 
From: "B M" <iamvirtual at gmail.com>
> On my ASR-33, an Anderson-Jacobson acoustic coupled modem (ADT-233) is
> installed.  Does anyone have information on this modem?  I have
> googled around, but have only come across the patent for the device,
> but no further information.
>
> I am looking to connect the TTY up to my ancient PDP-11 computer, but
> I need to be sure the modem is sufficiently disconnected for the
> direct connection.
>
When you look at the back of the ASR33, you will see 8 white connectors. 
Below these connectors you find a terminal block with 9 screws. The two 
leftmost are for the AC. Number 3 is Send+, number 4 Send-, number 6 RCV- 
and number 7 RCV+
Connect 4 to 6.
2 and 7 are brought out on a jackstik. This is to be connected to a current 
source of 20 mA, e.g. 160VDC and a resistor of 8K (10W).

Your now have a serial connection, 110 bps, 8 bits, 1 stop bit.

I know nothing about PDP, so what's written below is for a PC:

http://www.baudot.net/tty-connect/hardware.htm

This box comes between a PC COM port and the jackstick.

Nico