Practice code oscillator (CB21696E)

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

High voltage pulse generator (CB22480E)
This circuit generates pulses at a frequency that can be adjusted by a potentiometer. The circuit is...
455kHz Oscillator (CB21137E)
This oscillator uses a small IF transformer taken from an old transistor radio. FET admits...
Transistor relaxation oscillator (CB8041E)
Found in a 1970 EEE, this circuit generates signals that depend on the C1 capacitor. Transistors are...