Metal detector (T441E)

Found in a 1946s American documentation, this metal detector uses battery-powered tubes from the era. The circuit has great sensitivity.

Transistor Hartley Oscillator (CB4576E)
This circuit consists of a single Hartley oscillator using a bipolar transistor that can generate...
Safety Light (CB4785E)
This circuit turns on your car's backlight when a vehicle coming from behind gets too close to it...
30 to 45 MHz Receiver (CB20514E)
Used by the police this receiver tuned to the low VHF band. The circuit is from a documentation from the...