Receiving data via modem

[tdbeng]

Hello -- I'm working on a project where I can call my home phone number, and after 5 rings my home PC "picks up" via a modem. Then, I want to be able to enter in a series of numerical codes to change things on my PC. I'm at the point where, using VB and Hayes-compatible codes, I can call my phone and the the modem picks up. I'm using a standard external modem w/ 9600 baud serial to my Com port. But, if I punch in a few numbers, I can't get the modem to send data back to the PC (I can hear the DTMF and my voice through the modem speaker).

My question is: does a modem translate standard numerical incoming DTMF signals into ascii serial bytes that I can detect through the Com port? If not, can anyone suggest a way to do this (without having to design my own circuit)? Also, what type of handshaking has to occur in order to send out DTMF tones back to the incoming phone call (just to audibly verify certain steps in the VB app)? Thanks for anyone that can give me a quick lesson in modem protocol!

 

[IRstuff]

The answer, of course, is unfortunately no. The modem and DMTF are essentially unrelated except for the fact that they both must use the bandwidth available in a telephone line. If you need to send DTMF, you'll need to get a DTMF decoder, such as those available from CLARE:

http://www.claremicronix.com/datasheets/tone_signaling.html

although there are probably lots of other choices.

Likewise, you need a DTMF transmitter to send tones back to the sender.

Another option might be to find a phone that already does the conversion for you. TTFN

 

[Lewish]

Sorry, IRstuff, but I am going to disagree with you, a little. The modem will send DTMF tones when placing the call. Some have a command which will enable this ability, for testing, during the call. Screws up the data, but so what, you are testing.
Receiving DTMF is the real problem. I don't know of any modem command which will allow this.