High impedance millivoltmeter (CB20611E)

We found this circuit in an old American documentation. The components are from that period and may present difficulties in obtaining them.

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LED beacon (CB20490E)
This sole beacon which has a battery charged by photocells was found in documentation from 1991....
7 W amplifier TBA810 (CB15211E)
The supply voltage of this circuit can be between 4 and 20 W. The power depends on the voltage and the...
5 to 60 kHz FM Demodulator (CB25782E)
This 555 IC circuit was found in the November 1994 issue of Radio Electronics magazine. The...