[GreenKeys] ASR33

[Jim Haynes]

Depending on what kind of TTY interface card is in the PDP-11 you should
have no trouble.  The original, believe it was a KL-11, was designed to
connect directly to the ASR33 keyboard and printer.  This assumes, as
others have pointed out, that the ASR33 is just presenting the bare
current loop interface to the computer and not one that is powered.

Then DEC modified the ASR by putting a relay in series with the tape
reader magnet, and operating this realy from two more wires in the
cable from the KL-11.  This allows the computer to control tape reading.

The later single-line serial interface is the DL-11.  If I remember
correctly it could work with either RS-232 or current loop connections
to the TTY.

KL-11 is a three card item, with pots to adjust the baud speed.
DL-11 is a single card with rotary switches to set the baud speed.

The proper ASR33 for the PDP-11 is the private line model.  This has
a rotary switch line-off-local on the front, nothing in the call control
unit panel on top, and a plain screw terminal strip at the rear.
This is the simplest Model 33 there is.




jhhaynes at earthlink dot net