Found in a September 1972 Radio Electronics magazine, this circuit uses RCA's CA3020, a multi-purpose amplifier in a round metal 12-pin package.
This complementary transistor stage was found in a 1968 publication. The transistors are germanium types and...
Found in 80's Radio Electronics, this circuit uses an LED to indicate that a battery is being...
Found in Popular Electronics from 1969, this circuit uses a neon lamp from the time that had...