Patent GB-1096789-A (GB)
Title: Traffic detection apparatus
IPC: G01S13/92
Filed: 1965-04-13
Abstract: 1,096,789. Doppler radar. LABORATORY FOR ELECTRONICS Inc. April 13, 1965 [May 1, 1964], No. 15698/65. Heading H4D. The Specification describes a doppler radar system for supervizing the traffic flow on a one-way road 1, Fig. 1, whose direction may be changed, i.e. from A to B. Two identical antenna systems 4 and 5 radiate beams 6 and 7 respectively, the outward inclination of the beams' axes to the vertical being about 20 degrees, such that a vehicle 2 travelling in direction A first produces in the doppler radar associated with antenna 4, a positive highfrequency doppler signal corresponding to the leading edge of beam 6, followed by a negative low-frequency doppler signal corresponding to the trailing edge of beam 6. The doppler radar associated with antenna 5 then produces a positive low-frequency doppler signal and lastly a negative high-frequency doppler signal as the vehicle leaves the beam 7. The highfrequency and low-frequency doppler signals are extracted by means of respective filters and used to actuate relays such that a vehicle travelling in a prohibited direction is given a warning. In Fig. 3 traffic light switch 64 selects which direction of flow will be permitted and in the present case feeds power to green A direction light 67, to red B direction light 65, and to contact 86g of relay 86, such that B direction alarm 69 may be actuated on closure of contacts 86c and 86g. As a vehicle travelling in direction A leaves beam 6 the resulting negative lowfrequency doppler signal is filtered out and causes the energizing of relay 22, earthed contact 22a switches from contact 22b to contact 22c, wherbey light 76 is energized and relay 85 is energized via leads 90, 97, contacts 86b, 86c and lead 96. This in turn causes contact 85b to move from contact 85e to contact 85f, thereby respectively stopping relay 86 from being energized when the passage of the vehicle into beam 7 energizes relay 39, and the locking of relay 85, via lead 96, contacts 85b, 85e, 85f, 85b, now closed contacts 85d, 85a, lead 110 and contacts 115a, 115b. Contacts 85c and 85g also close, whereby, if switch 64 had been in its right-hand position, indicating that direction B was the correct direction, then alarm 62 would have been activated. As it is, a vehicle travelling in prohibited direction B will activate alarm 69. When the vehicle leaves beam 7 the negative high-frequency doppler signal energizes relay 36 causing the closure of contacts 36a, 36b and the energizing of relay 135 via contacts 36a, 36b, 39e, 39d and 22e, 22d. Relay 135 is locked on via contacts 135a, 135b &c. and contact 135c switches from contact 135d to contact 135c whereby capacitor 152 commences change up. After a time fixed by potentiometer 147 and proportional to the expected minimum distance between vehicles, the charge on capacitor 152 causes the righthand section of double triode 155 to conduct, whereby relay 115 is energized, contacts 115b, a release and relay 85 is de-energized. The system is now returned to its initial state to wait for the next vehicle. It is stated that ultrasonic instead of radio waves may be used.