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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Precision Current Voltage Converter with the CA3140 (CB12299E)
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This circuit works directly connected to the network and special care must be taken with its...
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Suitable for dual applications, this timer was found in a 90s Popular Electronics. The circuit...