Abstract: An interface circuit for use between a plurality of sensors, such as brush wear detecting sensors, and a single indicating alarm. The interface circuit is operable to transmit a signal from any or all of the sensors to actuate the alarm and latch it in its operative state until the alarm is de-energized by an operator.

Abstract: A brush wear indicator for an electrical machine including a holder for slidably mounting a brush, a self-winding, brush-biasing spring having one of its ends mounted in generally fixed operative relationship on the brush holder in combination with an indicating means electrically connected to either a contact, or a membrane switch, mounted on the relatively fixed end of the brush-biasing spring in a position such that it is contacted by a coiled portion of the spring responsive to the occurrence of a predetermined degree of brush wear. Such engagement is effective to actuate the signal means to indicate the predetermined degree of brush wear.