Found in a 1924 publication, this 2-valve receiver has a speaker output. Power comes from several batteries. Information about the coils is given.
This circuit is from a technical documentation from Texas Instruments from 1978. In it we have the...
We found this circuit in an old documentation, but it is still current, being able to feed sets of...
This circuit, found in a 1995 documentation, makes the relay bistable control from pulses of light...