Limiting circuit to control warning display indicators - compares the total circuit current with reference to limit activating of indicators

摘要

The control of display indicators in a central warning field of a data communications systems for monitoring disturbances is provided with a limiting circuit to ensure that in extreme conditions not all indicators are activated. The main control circuit controlling an indicator consists of a reset stage in the form of a flip-flop and a switching stage. The additional limiting circuit consists of a transistor controlled by a pulse generator. The total current used in the display field is coupled over a measuring resitor (Rm). A differential amplifier (DV) compares the measured valve with a reference set by a voltage divider (R6, R7). If the difference is negative and output is low and the transistor (Ta) is not influenced. However, if the current exceeds a maximum the display field is inhibited.