4 Jul
2015
4 Jul
'15
4:02 p.m.
Now to see if I can find out how to make a facsimile of the tape reader control gizmo
that DEC
used to allow the PDP 8 to control the paper tape reader, so I can get this terminal
properly
interfaced to the 8/e. In the meantime, I'm going to hook it up to the Altair 8800
for a little
immediate nostalgia.
Various companies had their own version of the reader control board, but they were all
much the same in
principle. A relay with contacts in series with the reader control circuit (the one that
operates the trip coil
at the back of the typing unit. The important thing is that it is a relay. In most cases
that reader control
circuit is not isolated from the mains power line. The relay, of course, provides
isolation between the
computer (coil) side and the contacts.
If you are tempted to use some more electronic solution you must preserve this isolation
,for example by
using an optoisolator. You do not want to give you and your 8/e a nasty shock.
-tony