27 Feb
2008
27 Feb
'08
3:16 p.m.
reminds me of the TRS-232
It was an aftermarket printer interface ("RS232") that operated off of the
cassette port of the TRS-80
There was a circuit for that in an old issue of Byte magazine. It was
daically just an Op-amp that detected the state of the cassette output
line. The output of said op-amp swung to the supply rails (+/-9V IIRC)
and was the RS232 output :-)
Also, didn't one of the early Radio Shack modems have a switch on it to
make the 'RS232' input actually the same levels as the Model 1 cassette
port, so you could use it with a plain Model 1 with no RS232 interface
(although with special software, of course)
-tony