18 Nov
2008
18 Nov
'08
12:56 p.m.
On 18 Nov 2008 at 19:34, Tony Duell wrote:
Well, that it curious. I would have thought very few
devices had +/-12V
supplies and a TTL level serial port (given the former, adding the
buffers to RS232 is trivial and cheap, and makes the device a lot more
useful).
I don't recall, except that I constructed a serial interface for an
MX-80 (might have been FX-80, I don't remember) and used a 6 v photo
battery to provide the negative signal levels for handshaking. It
was very simple and I may have picked up the circuit out of one of
the magazines of the time.
I believe that the IBM O&A has a schematic for at least one of the
Epson printers. That might provide some hints if anyone's curious.
Cheers,
Chuck