Abstract: Detection of lightning, storms, or the like via sensing means connected between an external antenna and ground, plus alerting means including gate means and indicator means operatively connected to the sensing means. An unpowered cascaded emitter-follower arrangement of at least a Darlington pair of transistors triggers the gate means when lightning-induced or similar fluctuations in ambient electric field cause the sensing transistors to conduct. A pulse-stretcher between the sensing means and the gate means controls the duration of indication and includes a capacitor connected to discharge through a sensing transistor during conduction of the sensing means and to recharge through a gate transistor during actuation of the indicator means. Resistors between the antenna and ground and between the base and the emitter of the respective transistors in the sensing means preclude actuation by fluctuations characteristic of slower-acting phenomena.

Abstract: Detection of lightning, storms, or the like via detecting means connected between an external antenna and ground, plus alerting means operatively connected to the detection means. An unpowered cascaded emitter-follower arrangement of at least a Darlington pair triggers a powered alerting circuit via an intervening gate opened when a fluctuation in ambient electric field causes the first transistor in such pair to conduct. A meter indicates such conduction even if the alerting means is not switched on, and alerting indicators in the alerting means may be tested in the absence of any detected field fluctuation.