Switching circuit for supervising the degree of wear of commutator-contacting carbon brushes

A circuit for supervising the wear of carbon-brushes normally making contact with a commutator of a direct-current electric motor of an electrically operated vehicle powered by an accumulator, including a main on-off switch for supplying power to said motor, electrically insulated control brushes carried by said carbon-brushes and movable therewith, and a warning signal indicator normally connected to said control brushes to provide a warning signal when said control brushes establish contact with said commutator upon a predetermined degree of wear of said carbon-brushes, said control brushes being connected to a memory means which controls said warning signal indicator and which is set when said control brushes contact said commutator, said memory means upon being set switches on said warning signal indicator independent of said control brushes contacting said commutator, and wherein a reset circuit resets said memory means upon activation of said main on-off switch, said resetting circuit comprising

• a delay means activated by said main on-off switch being connected to said warning signal indicator, said delay means switching on the warning signal indicator for a predetermined time interval independent of contact between said control brushes and said commutator, and said delay means resetting said memory means.