VITAL LEVEL DETECTOR AND {37 AND{38 {0 GATE CIRCUIT ARRANGEMENT EMPLOYING A TWIN-TEE OSCILLATOR

摘要

This disclosure relates to a fail-safe level detecting and AND gating circuit including a multistage solid state amplifier having a regenerative feedback loop. The regenerative feedback loop includes a frequency determining twin-tee network and a pair of voltage breakdown devices. The multistage amplifier produces a.c. oscillations when and only when the level of a d.c. voltage applied across each of the voltage breakdown devices exceeds its threshold value so that both of the breakdown devices become conductive and exhibit a low impedance condition.