Zero speed switch

Claim 1

IN A CONTROL CIRCUIT FOR A REVERSIBLE MOTOR: A STARTING RELAY HAVING A FIRST SET OF RELAY CONTACTS FOR ENERGIZING THE MOTOR FOR A NORMAL DIRECTION OF ROTATION; A PLUGGING RELAY HAVING A SECOND SET OF RELAY CONTACTS FOR REVERSE ENERGIZATION OF THE MOTOR, AND ENERGIZATION CIRCUIT FOR THE STARTING RELAY INCLUDING, IN SERIES, A NORMALLY OPEN MANUALLY OPERABLE START SWITCH, A NORMALLY CLOSED MANUALLY OPERABLE PLUG STOP SWITCH, AND NORMALLY CLOSED INTERLOCK CONTACTS OPERATED BY THE PLUGGING RELAY; HOLDING CONTACTS OPERATED BY THE STARTING RELAY FOR PARALLELING SAID FIRST START SWITCH; AN ENERGIZATION CIRCUIT FOR THE PLUGGING RELAY INCLUDING, IN SERIES, A NORMALLY OPEN MANUALLY OPERABLE PLUG SLOT SWITCH OPERATIVELY ASSOCIATED WITH SAID NORMALLY CLOSED MANUALLY OPERABLE PLUG STOP SWITCH, NORMALLY CLOSED INTERLOCK CONTACTS OPERATED BY THE STARTING RELAY, AND NORMALLY OPEN SPEED SENSING CONTACTS; HOLDING CONTACTS FOR PARALLELING SAID NORMALLY OPEN PLUG STOP SWITCH; A CONTROL RELAY FOR SAID SPEED SENSING CONTACTS; MEANS OPERATED BY SAID MOTOR FOR PRODUCING AN ALTERNATING ELECTROMOTIVE FORCE, THE AMPLITUDE AND FREQUENCY OF WHICH ARE FUNCTIONS OF THE SPEED OF THE MACHINE; A SERIES CIRCUIT INCLUDING A RESISTOR AND AN INDUCTIVE REACTOR CONNECTED ACROSS SAID ELECTROMOTIVE FORCE PRODUCING MEANS SO THAT THE VOLTAGE ACROSS SAID RESISTOR IS SUBSTANTIALLY A LINEAR FUNCTION OF SPEED AT LOW SPEED AND SUBSTANTIALLY CONSTANT AT HIGH SPEED; AND MEANS CONNECTING SAID CONTROL RELAY ACROSS AT LEAST A PORTION OF SAID RESISTOR FOR OPENING SAID SPEED SENSING CONTACTS AND INTERRUPTING THE CIRCUIT FOR SAID PLUGGING RELAY WHEN THE MOTOR SPEED APPROACHES ZERO.