TELECOM Digest OnLine - Sorted: Re: Hayes Smartmodems

Re: Hayes Smartmodems

Paul Coxwell (
Mon, 27 Jun 2005 10:05:02 +0100

> I'm confused. IIRC, the command was four characters, either
> ATDT or ATDP. Are you saying it would work with three?

You could use just ATD and if a mode which included dialtone detection
was in use, the modem would "adaptive dial."

It would attempt to dial the first digit using DTMF, then check to see
if dialtone was still present. If not, it would dial out the
remainder of the number as DTMF, otherwise it would switch to pulse
and start over.

I can't remember if it did this only after a reset (power-up or ATZ)
and then latched into tone or pulse mode for future ATD commands or
whether it tried DTMF every time. I have a SmartModem2400 somehwre in
a box with a manual, but might take a while to find!

> Also, for dialing out of a PBX, wasn't a 'pause' character needed to
> allow time for the second dial tone?

Yes, e.g. ATDP9,234-5678 where the comma indicates a default 2-second
pause. You could change the comma delay period via one of the

Again, in modes which included dialtone detection you could also
insert a W into the chain to tell the modem to wait for a new dialtone
before continuing.

- Paul.

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