Replacement elevator call button assembly

Claim 1

In an elevator operating circuit including a source of D.C. electrical potential at a first voltage, a pair of conductors upon which the electrical potential is normally impressed, and a touch-actuated gas tube connected across the conductor pair for producing a selected drop in the electrical potential therebetween to a predetermined second voltage when the gas tube is actuated so as to summon the elevator to a selected location and for maintaining the selected potential drop throughout an operating cycle of the elevator until the gas tube is subsequently deactivated by impressing a reverse polarity electrical potential upon at least one of the conductor pair at the termination of the operating cycle, a replacement unit for simulating the electrical operation of the gas tube and comprising, in series electrical connection across the pair of conductors: relay coil means energized upon actuation of said replacement unit and for enabling continued actuation thereof to the termination of the elevator operating cycle, lamp means for indicating an actuated condition of said replacement unit, zener diode means for providing a voltage drop between the pair of conductors when said replacement unit is actuated, and a parallel circuit comprising a normally open call button switch means for momentary closure to initially actuate said replacement unit by completing a series electrical connection including said zener diode means across the pair of conductors to provide the selected voltage drop therebetween, and normally open holding switch means operably associated with and for closure by said relay coil means for maintaining said completed series electrical connection when said call button means is opened after momentary closure thereof and throughout the remainder of the elevator operating cycle, whereby said replacement unit is deactivated at the termination of the elevator operating cycle by impressing a reverse polarity electrical potential upon at least one of the pair of conductors to de-energize said relay coil means, thereby opening said holding switch means to open said completed series electrical connection and enabling the electrical potential to risingly return from the second to the first voltage.