Re: dtmf problem!!
Hi,
The sequence you have to follow is:
1. Lift the handset, you will hear dial tone,
2. Before the dial tone stops, start dialing. The DTMF should last for at least 100 msec., then may be 100 msec gap ( I do not exactly remember now ), please check Application notes from Mitel or other DTMF IC Companies.
3. If the exchange has accepted your first digit, the dial tone should stop, and you should continue with dialling.
4. After the last digit dialled, you should hear ringback or busy tone on handset, you should keep the telephone OffHook all the time.
At which stage of the above sequence your dialing is failing?
I hope you have produced the correct pair (TWO) of tones for each digit. Square wave as such may not matter since the telehhone line will smoothen it out, but, correct frequency pair is important. Also. if you have a DTMF receiver IC like MT8870 or similar, you can make a circuit of that and connect your output to the IC and see if its digital output is correctly coming.
What respose you get from telephone line when you are dialling?
Regards,
Laktronics