4-tube reflex (T1662E)

This circuit that uses a loop antenna was found in a 1924 publication. The circuit has several supply voltages and sets of audio and RF coils.

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Latched TTL Switch (CB1474E)
We found this circuit in a 1975 radio amateur documentation. The circuit uses TTL technology and...
Easy Tuning Square and Sine Oscillator (CB4927E)
We found this circuit in an American 1980s documentation. The circuit can be assembled with modern...
Centigrade Thermocouple Thermometer (CB6023E)
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