> Its to go into a reed relay telephone switch from the 1960s. =A0If
> something went wrong it would print out

(? - the circuit you are building 'would' or the original circuit did this?
Presumably your circuit).

> ...what equipment was at fault by
> burning upto 90 lines onto electrosensitive paper. =A0I need to take the
> 50v from each "pen" and log which ones are live.
>
> Im sorry if Im not giving full details but some things you mention I
> havent a clue what they are. Like a shift register for example?
>
> Thanks for the help.

OK.
The thot plickens.
But, even now you have just given us one more smallish (but very
useful) dollop of information about what you are wanting to do.
There are still a few dollops missing.

If you can expand "it's to go into ... " into a fairly full
description we should be almost there!

eg are you trying to monitor the DRIVE voltages that drive 90 relays -
ie the voltages that cause the relays to operate.

OR are you trying to 'look' at the outputs of the relays to see if
they are operated or not, and they are switching 50 V.

Or

???

AND:
Are the voltages also connected to a speech circuit - ie will
connecting to the line to be monitored also connect to a circuit which
is carrying speech.
OR
Is there no actual speech signal on the actual wiring to be connected to.

Best of all, if you paint us a word picture of exactly what you are
wanting to do we'll be home .

Probably :-).
____________

Note that none of the questions were asking about shift registers.
Rather, some of the answers involved shift registers.
They still may be a good answer BUT it's looking like the opto-coupler
solution may be workable and, if so, it saves a lot of extra resistors
etc.



               Russell

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