555 Code Oscillator (CB26324E)

Found in a 1990s Popular Electronics, this circuit produces a tone on a small speaker. The keyer directly controls the power supply.

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Rocket Altimeter (CB25357E)
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Band rejector active filter (CB7405E)
This filter was found in Texas Instruments documentation from the 1980s. The circuit uses a common...
Transistor test (CB22545E)
16 commercial test circuit for tubes and transistors appeared in Radio Electronics magazine in...