Dear all,
I'm working on a circuit to control the water pump based on DTMF code and cellphone.
But the DTMF section is not working properly.
While sending the DTMF code, pin # 11 to 14 is on high and no change in state and pin # 16 is at low state.
This is the case for all DTMF codes which we are sending.
Kindly see the circuit and somebody please help me.

 

May be the gain of the 8870 is not high enough for your dtmf signal. Take a look at the link here..

http://forum.allaboutcircuits.com/showthread.php?t=79443&highlight=dtmf+decoder

Allen