A sensing edge for controlling movement of a door by actuation of a device upon an external force being applied to the sensing edge includes an elongated generally flexible tubular sheath secured to the leading edge of the door. The sheath has a longitudinal axis generally parallel to a leading edge of the door and includes an elongated hollow cavity extending generally parallel to the longitudinal axis, a first open end and a second open end. The sensor system includes a transmitter near the first end of the sheath for transmitting a signal through the cavity toward the second end of the sheath. The sensor system also includes a receiver near the second end of the sheath in alignment with the transmitter for detecting a signal at the second end and for generating an output signal upon detection of an absence of the signal when the passage of the signal through the cavity is blocked. The sensor system also includes a control circuit coupled to the receiver for receiving the output signal from the receiver and for sending a failure signal to the device only if no signal is received by the receiver for a predetermined time.