Practice code oscillator (CB21090E)

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

Active Switch (CB19851E)
This is a two-input audio switching circuit. The operational can be of any type and more entries can...
12 W Stereo Amplifier TDA1010 (CB14721E)
We found this amplifier for automotive use in the Philips integrated circuit manual from 1990. The...
FM Booster (CB22014E)
Found in old English documentation this circuit can be made with a BF245 or equivalent. Coils are...