Re: Substituting a modem for acoustic coupler

On 22 May 2006 12:06:50 -0700, brismith66@xxxxxxxxx <brismith66@xxxxxxxxx>
wrote:

My customer's application involves remote devices using an acoustic
coupler to transmit data to a host. The coupler is send-only: it is a cup
that fits over the phone's mouthpiece. It transmits at 1350 baud, 7E2.

My customer is introducing new devices into the field that won't support
an acoustic coupler; my job is to find a way to transmit data from the new
devices to the host. I need to co-exist with the existing devices.

Argh, I've beat my head against a few contracts like this. Just thinking
about it gives me a headache.

The first thing you need to do is determine the protocol in use. It's
likely not Bell 212A.

If you're lucky, it's Vadic protocol (Racal-Vadic manufactured the only
common 1200-baud acoustically-coupled modems and you could probably push
them to 1350). In this case you might be able to find some old Vadic modems
on eBay or something. You'll have to dig up documentation as well, since
Vadic modems didn't use the AT command set.

Otherwise, you'll just have to figure it out as best you can, though, to be
honest, you're probably not going to find hardware that supports anything
other than Bell or Vadic protocols (or you do and it's on an S100 card or
something).

If your situation is typical, the documentation for the hardware in use is
long gone...

If you can find a modem that will work, the next trick is talking to it at
1350 baud. Hopefully, this will only entail programming the UART properly.

.

Relevant Pages

  • Re: Substituting a modem for acoustic coupler
    ... coupler to transmit data to a host. ... For the user to transmit data, he dials a phone number, navigates ... My test lab is a PC with Hyperterminal; my modem is a spare USR ...
    (comp.dcom.modems)
  • Substituting a modem for acoustic coupler
    ... coupler to transmit data to a host. ... For the user to transmit data, he dials a phone number, navigates ... sends a voice prompt indicating success or failure. ...
    (comp.dcom.modems)