Philip.Belben_at_powertech.co.uk wrote:
>
> Tony Duell wrote:
>
> > I'm pretty sure the teletype is a passive device and expects the other
> > device to source the loop current.
> >
> > 5V should be enough for the transmitter loop (which is just switch
> > contacts), but I doubt if it would be enough for the receiver loop (more
> > like 12V or more here)
>
> I used a TTY ASR-33 as a printer for my PET years ago. My memory is
> that if I left the receiver open circuit, i yammered away printing
> nulls; if I shorted out the loop it didn't. I interfaced it using one
> transistor - no power supply was necessary.
>
> +----------------------
> |
> OUT b |/c
> -------/\/\/\/---------| NPN TTY
> |\e
> PET |
> -------------------------+----------------------
> GND
>
> Note: I never interfaced the TTY transmitter - not even for reading
> paper tape (don't know why not)
>
> Philip.
Well, I tried this out, and to my surprise it did indeed wor
(that is, shorting the wires.) Now I just have to look in my
box of odds and ends to find the parts to make this little
interface.
Thanks,
Edward
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Received on Wed May 13 1998 - 15:06:52 BST