🚀 go-pugleaf

In article <6LRgPB4w165w@bluemoon.rn.com> gerry@bluemoon.rn.com (Gerard M. Foley) writes:

>   Since it seemed busted anyway, I just now pried it open.
>I have not finished tracing the schematic diagram of it,
>but believe it or not, it containes the following parts,
>and no more:  1 Dual Op-Amp  5 resistors  4 diodes 4
>capacitors! (Sorry for the spelling of "contains" up
>there).  There's magic in electronics!

The magic is mainly in software, because most decoding of the
fax signal is done in software. That's what I think.  I have seen 
a shareware program called Hamcomm, which can send and decode 
morse, rtty etc. signals. The circuit needed for decoding contains one
Op-amp and some passive components. The circuit filters the incoming
signal and converts it to square wave, which is send to one of the input pins
in the serial port. Every time the state in that input changes, UART
generates an interrupt. The software measeres time between interrupts
and so determines the signal frequency. When the program is used for sending,
the PC speaker ouput is connected (via passive low-pass filter) toi the
transmitter. Quite a hack.
I think that the fax device you mentioned works in the quite same way.

 
--

Tomi.Engdahl@hut.fi            "Don't force it; get a larger hammer"
then@vipunen.hut.fi