sharing modem and fax on 1 line

[Greg A. Woods]

In article <1990Feb22.174344.19266 at druid.uucp> darcy at druid.UUCP (D'Arcy J.M. Cain) writes:
> In article <25e307cd-3b6comp.unix.i386 at ddsw1.MCS.COM> akcs.richie at ddsw1.MCS.COM (Richard Schwarzbach) writes:
> >sharing of a single phone line between a FAX and a MODEM.
>
> There is actually a device which will handle this transparently to the
> user.  When the phone rings, it puts the line off hook but continues
> to send the ring tone so that it seems like the phone is still ringing.
> It then tries to do FAX handshaking.  If successful it connects to the
> FAX line otherwise it connects to the modem line (or voice I suppose)
> and the fake ringing stops.

I considered building one, but it's not as simple as it sounds.

Your intermediate device must replace a good part of either your FAX or
modem, since it is very difficult to pass off a call once you have
already done the handshaking necessary for either connection.  Once
you have negotiated the call, you are stuck.

It may be possible to try detecting the originate tone of either
device while generating ring to both devices.  Upon recognizing the
tone, check that the desired device has gone off hook, and then
connect the call to it.  This was the approach I was working on anyway.

Our FAX (Toshiba, I think) tries to connect, then rings its handset if
the connect fails.  Unfortunately it does not ring the downstream
phone line too, though I suspect it would be too late anyway.

My simplest solution was to put a timer switch on the FAX, and have it
simply shut off after business hours.  The FAX electronics are smart
enough to make it transparent to the downstream phone when the power
is off.
-- 
						Greg A. Woods

woods@{robohack,gate,eci386,tmsoft,ontmoh}.UUCP
+1 416 443-1734 [h]   +1 416 595-5425 [w]   VE3-TCP   Toronto, Ontario; CANADA