Found in a 1924 Gernsback publication this circuit uses 4 batteries for power and loop antenna. Listening is over a high-impedance type earphone or loudspeaker common at the time.
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...