Astable 555 (CB21101E)

This 50% duty cycle configuration was found in a Popular Electronics from the 1990s. The operating frequency is given by C1.

CMOS Oscillator (CB25040E)
This circuit is from Radio Electronics from February 1987. The frequency is given by the crystal that...
LASCR Controlled Oscillator (CB13888E)
In this circuit, a light-sensitive SCR or Light Activated SCR determines the operation of an...
Hearing Aid Amplifier (CB21798E)
This 3-transistor circuit was found in a Mullard manual from 1960. The transistors are germanium of the...