ard(a)p850ug1.demon.co.uk (Tony Duell) wrote:
I also got a right odd looking thing - it's a (or at least looks like a)
ZX81 peripheral. There's a crystal on it as well as 3 chips, 4060, 4040 and
4087 and its marked 'G4IDE' or 'G41DE' on the front and 'FAX PCB'
on the
Those chips are all standard 4000-series CMOS (the 4040 and 4060 are
counters, I forget what the 4087 is). Drawing out the schematic should
take < 1 hour...
back. Since I don't believe anyone produced a
FAX add-on for the ZX81 I'm a
bit puzzled!
G4IDE looks like an English amateur radio callsign to me. I suspect this
is some kind of amateur radio/weather (?) analogue-type fax image
decoder, and has nothing to do with modern fax sent over telephone lines.
Are there any connectors on the PCB (other than the edge connector to the
ZX81)?
Hi
Although only about 6 years ago, I thought I'd mention that
related to weather FAX, I'd wrote some software that would
convert one of the softmodems ( Cardinal and Digicom ).
You need a receiver with a BFO. It did a little simple
DSP filtering and then a zero cross detector for the FAX.
It used some freeware software, from the net, to display on
a PC. If there is any interest, let me know.
It would make sense that on a machine without extra counters,
one might add a counter to find time between zero crossings
for the frequency detectors.
Dwight
Dwight