42 kHz oscillator (CB21805E)

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

Micro Power LED (CB15111E)
This circuit causes an LED to flash at a frequency determined by the capacitor. The circuit has an...
Analog frequency meter (CB7918E)
Found in American documentation from the 90s, this circuit can measure frequencies on a linear...
FM Optical Transmitter (CB5269E)
This frequency modulated light transmitter is from a 1990s documentation. The circuit may use...