Abstract: Detection circuitry in which the range and signal to noise ratios are improved includes a plurality of light emitting diodes connected in series and a plurality of photodiodes. Each photodiode has its own separate detection circuit which is AC decoupled by capacitors. Summing circuitry is connected to sum the outputs of the detection circuits and the resultant signal is fed to an output device. The magnitude of the output signal is increased by a factor equal to the product of the number of light emitting diodes and the number of photodiodes, over the situation where only one diode of each type is used.

Abstract: An elevator car, supports a pair of sliding car doors which can be moved in synchronism towards or away from one another to close or open. An elongate detector strip is mounted on the outer face of respective car doors adjacent the leading edges thereof. A pair of opposing landing walls support respective ones of two sliding landing doors. The landing doors are synchronized to open and close with the car doors by control circuitry. The detector strips together define three separate regions in which detection of an obstruction can take place namely, a column like region extending across the leading edges of the car door and the landing door a column like region extending across the leading edges of the car door and the landing door, and a planar region extending vertically between the detector strips.

Abstract: A movable door incorporates a proximity detection system for sensing obstructions in the path of the door. The system comprises an array of transmitter/receiver pairs (21, 22 and 23), each pair comprising a transmitter (1) for transmitting an energy pulse, a receiver (2) located adjacent the transmitter and directed to receive any reflected transmitter pulses, and a shielding (3) for shielding the receiver (2) from receiving energy pulses directly from the transmitter (1). At least two transmitter/receiver pairs (21, 23) are mounted on a leading edge or face of the door (12) to transmit energy pulses in a direction which is not at right angles to the leading surface or edge of the door, to monitor for obstructions in the path of the door (12). Another two transmitter/receiver pairs (26 and 28) are mounted on the leading edge or surface of the door (12) to transmit energy pulses at right angles to the surface or edge of the door (12).

Abstract: A movable door incorporates a proximity detection system for sensing obstructions in the path of the door. The system comprises an array of transmitter/receiver pairs, each pair comprising a transmitter for tranmitting an energy pulse, a receiver located adjacent the transmitter and directed to receive any reflected transmitter pulses, and a shielding for shielding the receiver from receiving energy pulses directly from the transmitter. At least two transmitter/receiver pairs are mounted on a leading edge or face of the door to transmit energy pulses in a direction which is not at right angles to the leading surface or edge of the door, to monitor for obstructions in the path of the door. Another two transmitter/receiver pairs are mounted on the leading edge or surface of the door to transmit energy pulses at right angles to the surface or edge of the door. Different transmitter/receiver pairs may transmit on different frequencies, and means for suppressing unwanted reflected signals is provided.

Abstract: A system for synchronizing pulse signals transmitted between two stations using only two conductor lines includes a synchronization circuit. The circuit includes two modulators and two EXCLUSIVE-OR gates for controlling when data pulses are transmitted and when synchronization pulses are transmitted.

Abstract: A detection system for a sliding lift or elevator door comprises at least two sensors for monitoring the door opening. The sensors are arranged to detect the presence of a moving irregular shape (e.g. human form) in the doorway to reverse the opening action of the door or, if already open, to prevent the door from closing. A signal compensation circuit is provided to process the output signals from the sensors in a sense to maintain the outputs equal under steady state conditions. This is achieved by using the output of a first sensor as a reference signal. A comparator compares the output of a second sensor with a reference signal and through a feedback loop modifies the output of the said second sensor in a sense to equal the output of the first sensor. The feedback loop contains a delay circuit which is switchable between a long and a short delay. For slow changes in the output of the second sensor the long delay is effective but for first changes the delay circuit is switched to provide a short delay.