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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Rectangular Pulse Generator (CB18915E)
This circuit uses a unijunction transistor in a different configuration to generate rectangular pulses at...
TTL Logic Tester (CB13785E)
We found this configuration in a 1974 technical documentation. It can test both TTL logic circuits and...
Transmitter Power Meter (CB13273E)
We found this circuit in an old American publication. The circuit is designed to measure the...