Found in a 1992 book, this circuit is intended for operation with audio signals. Equivalent operational amplifiers can be used. The optical coupler is an unusual type today.
This circuit oscillates at a frequency of 0.5 Hz. We can find it in an American documentation from the...
We found this HV generator circuit in a 1967 publication. It can be fitted with SCR TIC106 and the...
Connected to a shortwave receiver, this circuit is intended to enable the decoding of signals in...