The present invention concerns a communication system with monitored input state of an input device. The input device has an input connection, a ground connection and an input circuit connected between the input connection and the ground connection. The input circuit is designed to detect an input signal. A sensor device is also provided, which is connected to the input connection and optionally the ground connection. The communication system also has a current-increasing device connected to the input connection and the ground connection, which is designed to furnish an increased current for the input circuit for an adjustable time period as a function of the voltage lying on the input connection. A power supply is also provided to supply power to the sensor device.