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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Sequential Back and forth (CB17123E)
We found this circuit in an old documentation, but it is still current, being able to feed sets of...
Polarity Protector (CB10450E)
This circuit was obtained in a 1977 magazine, but it can still be easily assembled, as the...
Optical communication transmitter (CB7849E)
This circuit was found in a 90s American documentation. The circuit uses an LED that can be of a...