Abstract: A monitoring system for detecting faults in an apparatus, such as a ski lift, employs a communication network onto which a sensor bus controller periodically transmits a safety message and receives a echo of each safety message. Different sensors are coupled to sensor adapter modules that in turn are connected in a series to the communication network. After the last sensor adapter module in the series, each safety message is echoed back along the communication network. Each sensor adapter module, upon receiving a safety message, increments a count in that message and transmits the resultant safety message to another module. When a sensor indicates a fault condition, the associated sensor adapter module blocks propagation of safety messages along the communication network. The sensor bus controller determines, in response to a failure to receive the echo and to the count in the echo, whether a fault occurred.

Abstract: A monitoring system for detecting faults in an apparatus, such as a ski lift, employs a communication network onto which a sensor bus controller periodically transmits a safety message and receives a echo of each safety message. Different sensors are coupled to sensor adapter modules that in turn are connected in a series to the communication network. After the last sensor adapter module in the series, each safety message is echoed back along the communication network. Each sensor adapter module, upon receiving a safety message, increments a count in that message and transmits the resultant safety message to another module. When a sensor indicates a fault condition, the associated sensor adapter module blocks propagation of safety messages along the communication network. The sensor bus controller determines, in response to a failure to receive the echo and to the count in the echo, whether a fault occurred.