We found this circuit in a 1964 Electronic Design. The triac and SCR can be replaced with modern equivalents according to the load. The circuit is for 160V network.
Using a common crystal diode and a 741, this circuit can be used to detect microwaves. The circuit is...
The two circuits shown show how to obtain an SSB / CW control for receiving this signal top at a...
The oscillation of the relay causes the applied audio signal to deform and start to resemble the...