Metal detector (T441E)

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

Converting Calculator to Stopwatch (CB5095E)
This circuit is connected to the sum key of a common calculator. Adjusted to produce a pulse per...
20 MHz Colpitts Oscillator (CB5122E)
This circuit can generate signals in the range from 1 to 20 kHz, depending on the crystal. The...
Unregulated Power Source of 6 and 9 V - I (CB1167E)
This simple, unregulated power source with full-wave rectifying is for small appliances that do...