Code practice oscillator (T380E)

This oscillator was found in the 1961 RCA tube manual. Similar configurations appear on this site for manuals from other times by the same company.

Record Head Preamplifier (CB4949E)
This 80's circuit can be used in media recovery. The integrated circuit is of the time, but modern...
Balance Indicator (CB5021E)
This circuit is from the American magazine that no longer exists Science & Electronics,...
Quail Brooder (CB4467E)
This circuit, from a 1988 documentation, consists of an automatic temperature control using an NTC...