Caller ID

[admin]

Although not a question specific to microcontrollers, I'm going to ask here anyway in hopes that someone has tried this and can tell me if it works. (Actually, I'll be using a 9S08SH8 and a CMX867A DTMF/FSK chip so this should be kinda on-topic.)

During a phone call I want to send a caller ID packet from my device to a distant phone with a caller ID display. Will that work? I notice that when I'm on the phone and get a call, my ear gets blasted into near deafness by the incoming caller ID data. It is extremely loud. Is this necessary for me to send and display a caller ID string, or do you think I can do it with "normal" audio levels? Or is there anything else that may prevent this from working?

My objective is to interrogate my uC device with a standard caller ID phone and display the results, without using any special hardware on the caller's end (other than a caller ID phone handset).

Thanks for any comments & suggestions.

[admin · Accepted solution]

Yes, it works!

[tonyp]

Caller ID (in my niche of the world) is sent before the phone answers (usually between first and second ring).  ISDN is a different case.

Although "call waiting" may show Caller ID also, this info bit is sent during a short break in the communication, not while you're talking.

There are several different implementations of Caller ID (for various countries), so I'm not sure if what I say here applies in your case.

But, I think it would not be possible to use an ordinary phone's caller id screen because, if that phone works correctly, it should NOT listen for the Caller ID string during off-hook.  (If it did, wouldn't it be possible for someone to spoof the ID with another number?)

To do what you want, maybe you could use a voice chip (e.g. ISD) to have your application talk back to you.

[admin]

If you buy the feature of "Caller ID on Call Waiting" from your phone company, they do indeed send the caller ID while your phone is off-hook when you get a call while already in a call. I don't see why I can't send the same information and have it display my stuff. The thing is, the caller ID data is sent many many times louder than normal speech, so I'm not sure if I can make it work if it has to be at that high level. I was hoping someone has done this before. I hate to (try to) blaze a new trail if I don't have to.