mpratap@CUE.BC.CA (Matt Pratap) (03/25/91)
We have a semi-malfunctioning modem for dial-ins that refuses to re-connect at 2400bps after someone connects at 1200 bps. The only cure for this is to turn it off then turn it on. What I am looking for is a circuit to cut power for about 2 seconds after someone disconnects. Or even better, cycling the power after someone disconnects at 1200 bps. With my limited electronics experience, I figure a JK flip-flop, a 555, and a relay or power transistor should do the job. The power in (to the modem) would go thru this circuit and then to the modem. Has anyone done something like this? Thanks ------------------------------------------------------------------------- Matt Pratap, Victoria B.C. -=- mpratap@cue.bc.ca * (Insert quote here!) ------------------------------------------------------------------------- P.S. Can you guess what brand of modem this is ? :-)
bender@oobleck.Eng.Sun.COM (I want to be eating rich soup in another town) (03/25/91)
In article <9103242112.AA22375@cue.bc.ca> mpratap@CUE.BC.CA (Matt Pratap) writes:
->We have a semi-malfunctioning modem for dial-ins that refuses
->to re-connect at 2400bps after someone connects at 1200 bps.
->The only cure for this is to turn it off then turn it on.
->
->What I am looking for is a circuit to cut power for about 2 seconds
->after someone disconnects. Or even better, cycling the power
->after someone disconnects at 1200 bps.
->
->P.S. Can you guess what brand of modem this is ? :-)
I'll bet it's a CTS modem, right? My school bought a load of these (because
they were cheap). We first started out buying the ATD model, which used
some really screwy proproetary(?) command set, (not the Hayes or Racal-Vadic
set), but used them just for dial-in on our VAX. They were good for a few
months at least before they started dropping like flies. We routinely had
twice the number of modems we used for dial-in in the modem rack; half were
spares and were already cabled up to power so that when a modem went down,
the sysadmin would just switch the phone and serial connections to one of
the "good" (but not for long!) modems and take the bad one out and
downstairs to the tech shop for repair. When we started wanting to dial
OUT, we realized that the ATD models wouldn't work very well, especially
with PC and Mac communications programs because of their stupid command set,
so we bould a lod of ATH modems; the same as the ATD units, but with the
Hayes command set. Reliability was as "good" as the ATD units. Most of the
problems we had with the CTS modems (both models) were when they were used
for auto-answer on both a VAX and several of our campus UNIX systems; the
modems would answer the phone, but not connect at 2400 baud, only 1200
sometimes, other times they wouldn't answer the phone at all because they
got too hot, and you had to either power-cycle them, or leave them off for a
few hours, obviously not a very good solution in an unattended dial-in
environment! The best modems we had for dial-in were the old Penril
1200-baud modems; built like a tank out of a heavy extruded ALUMINUM case,
never got hot, and never failed us. I think these were the same modems that
Bell used to lease to customers.
mike
--
Won't look like rain, Won't look like snow, | DOD #000007
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We just can't tell you anymore, We've never made oobleck before! | MSC #298726halco@iccgcc.decnet.ab.com (03/27/91)
In article <9103242112.AA22375@cue.bc.ca>, mpratap@CUE.BC.CA (Matt Pratap) writes: > We have a semi-malfunctioning modem for dial-ins that refuses > to re-connect at 2400bps after someone connects at 1200 bps. > The only cure for this is to turn it off then turn it on. > Apologies if this doesn't apply or if you already know... If it's a Hayes-compatible modem, this is normal. The speed can be reset by sending an "AT" from your computer at 2400bps at the end of the call.