I am new to electronics and learning as I go. My project is a DTMF receiver working off a cell phone and activating a series of relays. The integrated circuit that was called for was a CM8870, which was not available and was substituted by the NTE 1690. An ear piece connected to the cell phone and the wires to the ear plugs were cut to allow one wire as input to the IC and the other for ground. After dialing and then pressing a number on the phone nothing happens. There is no current from the phone to the IC. As I said I don't know much about this, can anyone give me a hand?
thanks