In this 1968 circuit the approach of the key which is a circuit tuned to the tube oscillator causes the relay to lock. The relay is of high voltage type and the secondary of the transformer is approximately 150 V.
In this 1968 circuit the approach of the key which is a circuit tuned to the tube oscillator causes the relay to lock. The relay is of high voltage type and the secondary of the transformer is approximately 150 V.
