We found this circuit in the Electronics Experimenter Handbook magazine from 1993. L1 has 2 = 2 turns of 28 or 30 wire in the shape of 0.5 cm without core. The range reaches a few tens of meters.
Found on 80's Popular Electronics this circuit operates at 455 kHz. The explorer coil is formed by...
This high-precision circuit was found in a 1969 documentation. The components are from the period. R1...
This bistable or flip-flop is triggered by a negative pulse applied to the collector of the...