SYSTEM AND METHOD FOR TRANSMITTING DATA IN AN OPTICAL TRAFFIC PREEMPTION SYSTEM

• Main Author: STEVEN M. HAMER
• Format: Patent
• Language: English
• Published: 29.04.1993
• Subjects: ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; PHYSICS; SIGNALLING; TRAFFIC CONTROL SYSTEMS; TRANSMISSION

An optical data communication system (10) for transmitting a stream of light pulses (30), including both priority pulses (32) and variable data pulses (34) from an optical emitter (24) atop certain vehicles (20, 22, 24), such as police cars, etc., to a detector (16) mounted along a traffic route. The method allows variable data (32) to be transmitted in a stream of light pulses (30) along with priority pulses (34). The variable data can include an identification code that uniquely identifies the emitter, an offset code that causes a phase selector to create a traffic signal offset, an operation code that causes traffic signal lights to assume at least one phase, and a range setting code that causes a phase selector to set a threshold to which future optical transmissions will be compared. Phase selectors (18) separately identify received priority and data pulses and assemble data derived therefrom. The data may include a discrimination algorithm for tracking a plurality of optical transmissions with each detector channel. The optical emitters may also be provided with a coincidence avoidance mechanism which causes overlapping optical transmission from separate optical emitters to drift apart. The optical signal format allows variable data to be transmitted while maintaining compatibility with prior optical traffic preemption systems.