Practice code oscillator (CB21090E)

Found in Popular Electronics from the 90's, this circuit consists of an audio oscillator for Morse code practice.

Symmetric Power Supply (CB16761E)
This power supply was originally created for the CB16760E (Loudness System) but can be used in any...
Unidirectional motion sensor (CB7281E)
Found in 1980s Electronic Engineering, this circuit uses common phototransistors as sensors. The...
Simple Symmetrical 6 V Power Supply (CB20207E)
This simple, unregulated power supply with an approximate 6 V output voltage can supply currents up to...