Line current regulating stage for alarm indicator - is controlled directly by impedance changes of line and ensures sufficiently high alarm current

摘要

An alarm system is provided with a regulation stage to limit the current during standby and activated conditions to predetermined values. Each alarm line (1) is assigned a sensor state (2) with an output (A) and an operating terminal (B) receiving a 12V supply. Resistors (R1, R2) are sized to provide bias for the base and emitter of a transistor (T1) and the voltage for the alarm standby condition. The unit controls the current to an indicator (3) alarm. The sensor stage ensures a sufficiently high line current for a clearly recognisable operation of the indicator-secondary alarm (3) in the alarm condition.