We found this circuit in an American documentation from 1947. The circuit uses 5 tubes and has a feature to keep the tube filaments preheated.
This circuit was found in a 1967 General Electric documentation. The circuit generates signals...
This interesting effect circuit was found in a 1982 publication. The sequence of musical notes is...
This circuit is from a 1969 General Electric manual. The SCR may be the TIC106. Similar circuits...