3-channel preamp (T484E)

This 4-tube circuit was found in an American publication from 1947. It is intended for audio distribution lines using a transformer source.

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Crystal Radio (CB22169E)
This 1960s receiver uses a germanium diode as a detector. The phone can be crystal or high...
Leak alarm (CB6958E)
This circuit is from Popular Electronics. The buzzer is of the Sonalert type with built-in...
Timer 555 (CB18645E)
This basic version of the timer with the 555 was found in documentation from the 1980s. The relay...