Electronics Eavesdropping Device Detector

[globby]

I really have trouble with a section of the electronics eavesdropping device detector in this site.
I cant tell whether the portion on the picture is a detector or whatever. I really want you guys to tell me more about this circuit, describe the work of this circuit and examples.
I want you guys to respond as soon as you can
The attached file is given below

[audioguru]

Hi Globby,
People who built the project found that it doesn't work. Its first opamp has a lot of gain but does not have an input offset voltage nulling trimpot so frequently with no input signal the voltage controlled oscillator oscillates all the time, or if the offset is negative then the circuit is not sensitive.

If you are lucky and find a quad opamp with a very low input offset voltage then the circuit might work if you make a few changes (as you found, the AM detector is very strange so I fixed it).