Emergency stop circuit monitoring system

A power supply circuit including a number of sections in which possible faults are to be detected, having a monitoring circuit including a parallel monitoring line and a number of impedances each connected between a respective section of the power supply circuit and the parallel monitoring line so that the total operative impedance of the monitoring circuit is dependent upon the number of the impedances connected to live sections of the power supply line and is thus indicative of the position of the fault.

A monitoring system for an energency stop circuit in which any one a plurality of energency stop buttons may be actuated at various remote locations in the circuit to break the circuit, the monitoring system being adapted to indicate the region of the open circuit condition and comprising:

• means for generating an analogue voltage related to the position of the open circuit condition, a series chain of impedance elements which is supplied with a voltage at least equal to the maximum value of the analogue voltage, a corresponding number of comparator devices each having one input connected to a different junction of the chain, and the other input connected to the source of the analogue voltage;
• and a corresponding number of voltage sensitive indicating devices, each indicating device connecting the output of one comparator to that of the next comparator, so that any indicator device which is connected between two comparator outputs which are both "low" or both "high" will be in an "off" condition, but an indicator device which is connected between the outputs of two comparators which are at different levels will be in an "on" condition.