42 kHz oscillator (CB21805E)

This circuit was used as an eraser for old tape recorders. The circuit is from a 1960 Mullard transistor manual.

Digital Capacimeter (CB16780E)
The accuracy of this 3-digit digital capacitor meter depends on the tolerance of the components used and...
Battery Charge Indicator (CB26002E)
This circuit was found in the March 1997 Electronics Now magazine. It uses a common analog...
Four Transistors Reflex Receiver (CB18301E)
This is a diagram of a 1958 commercial receiver. The circuit was found in documentation at the...