Thanks for the quick response.
However, please note that it is not dialing tone I'm trying to detect but rather a off-hook tone consisting of the frequencies 1400, 2060, 2450 and 2600 Hz. My schematics is exactly the same as depicted in the first post on this thread (only I did connect the input line via a capacitor) with proper components values .
I guess my question is this, does it make any sense that I read 2V on my LM567 input pin when it is not connected to anything? Isn't it suppose to be floating? Does it mean I have a problem with the ic itself?
Thanks