We found this 6-tube amplifier in a 1947 publication. It is a Public Address amplifier with excellent performance using triodes on the output.
Found in an American documentation from 1969, this astounding circuitry makes a relay operate on 3 Hz...
This circuit may be modulated by a very low frequency signal, for example to obtain the vibrato...
This circuit was found in Delco documentation from 1966. The components are from that time....