[GreenKeys] Current Loop or RS232?

[tony.podrasky]

Yes,

What you'll need:

o 9-Volt battery.
o 1K resistor.
o Clip leads.
o Simpson Analyzer (multi-meter / oscilloscope)
o Pin-out of a standard DB-9 / DB-25 - or whatever
   kind of connector you have.

If you can find a pin-out for the connector you'll be
way ahead, if not give this a try.

Ground the meter. Check each pin on the PDP8's I/O port
and see if any have about 12 volts on them. If so it's
probably RS-232.

Now, YOU'LL have to write a small program that checks for
interrupts. If you can do that, the next thing we'll go over
is grounding one end of the 9-v battery, and connecting the
1K resistor in series with the other end and touching it to
each pin of the connector - and watch for the program to halt.
If it doesn't halt, flip the battery around and try again (because
RS-232 is pretty much +12v and -12v.

Let me know how that goes.

UE,
K2EAA - TONY
NNNN
ZCZC


On 09/15/2017 02:43 PM, Paul Heller wrote:
> After looking a long time I finally got hold of a PDP8. I got it from
> another ham. The guy I got it from said he used to have a teletype
> hooked up to it.
>
> Is there a way I can determine if it is a current loop or an RS232
> interface?  I assume if I guess wrong I could damage the teletype or
> the terminal board in the computer. Is this a valid worry?
>
>
> Thanks for any help. I'm a newbie to DEC computers. Maybe I can
> finally put that tape relay in my teletype to good use.
>
> Paul ______________________________________________________________

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