Call registration and acknowledgement system for an elevator and method of testing such system

In an elevator system having an elevator control for controlling an elevator car in a hoistway, a call registration and acknowledgement system, comprising:

• call registration means remote from the elevator control for transmitting a request signal to request elevator service;
• the elevator control inluding an input/output port and means for latching the port at a voltage level when a signal is coupled thereto, the latching means including a triac connected between the input/output port and ground potential having a gate electrode and means coupled to the gate electrode for generating a gating signal, the elevator control further including a resistor connected to the input/output port, a switch for selectively coupling the resistor to either first or second voltage levels, and means coupled to the switch and to the triac for operating the elevator control in a test mode to determine the operability of the elevator control and the call acknowledgement means;
• a single wire connecting the call registration means to the input/output port so that the port is latched at the voltage level when a request signal is developed;
• and
• call acknowledgement means remote from the elevator control connected to the single wire and actuable in response to the latching of the port to acknowledge a request for elevator service.