Patent ID: 7407048

Claim:
A safety circuit for a passenger conveyor having a drive system, comprising: a plurality of controllable switches, each switch of the first plurality of controllable switches being responsive to a functional unit associated with the passenger conveyor to produce a first switch output signal having a first state if the functional unit is operating properly and a second state if the functional unit is malfunctioning; a controller apparatus including: a plurality of input terminals each coupled to a respective one of the switches for receiving the respective switch output signals; a plurality of interrupt switches, each interrupt switch being arranged in electrical series to conduct a drive enabling signal for the drive system when all of the interrupt switches are in a closed state, each interrupt switch being coupled to a respective one of the input terminals and being opened in response to a respective first switch output signal having the second state to interrupt the drive enabling signal to stop operation of the drive system; a redundant interrupt switch arranged in electrical series with the plurality of interrupt switches, wherein the series connection of the redundant interrupt switch and the plurality of interrupt switches has an output producing a second out signal having a first state if all of the interrupt switches and the redundant interrupt switch are closed and a second a state if any one of the interrupt switches and the redundant interrupt switch is open; and a controller arranged to monitor the state of the first switch output signals of the plurality of controllable switches and to monitor the state of the second output signal, the controller sending a signal to open the redundant interrupt switch when the signal state of the any one of the first switch output signals has the second output state and the second output signal has the first signal state.