Alarm and circuit defect signalling device - differentiates between defect and alarm signals using different polarities

摘要

The circuit defect signal is of opposite polarity to that of the alarm signal and provokes the blocking of the common emitter connected input transistor (12) which is normally biased at half the total voltage when the alarm signal tends to increase its conduction. The circuit has a feedback loop circuit (1) comprising a transistor, complementary to the common emitter transistor, whose collector current constitutes the base current of the input transistor. The change of state of the input transistor puts either the transistor producing the alarm signal or the transistor producing a defect signal into a conduction state.