Practice code oscillator (CB21696E)

In the figure we have an astable multivibrator driving a speaker to produce audio signals for Morse code practice.

Telephone Amplifier (CB18148E)
This simple telephone amplifier can be used as an auxiliary amplifier for additional listening, without...
TTL Optical Link (CB23670E)
This circuit can be used in fiber optic links or even direct links to microcontrollers and other...
Twilight Switch (CB11511E)
This article was obtained in a French magazine Nouvelle Electronique from 1994. It can be easily...