Patent GB-941921-A (GB)
Title: Traffic speed monitor
IPC: G01P3/60
Filed: 1959-12-02
Abstract: 941,921. Road vehicle counting and indicating apparatus. LABORATORY FOR ELECTRONICS Inc. Dec. 2, 1959 [Dec. 2, 1958], No. 41013/59. Headings G4A, G4D and G4Q. In apparatus for use in a road traffic control system means are provided for counting on a counter the number of successive vehicles which are travelling at speeds greater than or less than a predetermined speed according to the mode of operation of the apparatus, an output being produced when a predetermined value is attained in the counter. The apparatus described in Specification 929, 631 may be employed to provide, for each vehicle detected, a vehicle presence pulse on a lead A and a pulse on a lead B whose amplitude represents the vehicle's speed. The arrangement described operates in an "above" mode in which successive speeds above a predetermined speed are counted, or a "below" mode in which successive speeds below a predetermined speed are counted, the mode of operation being selected by adjusting an operation selector 20 comprising three ganged two-position switches 5, 6, 7 and the predetermined speed being selected by adjusting a potentiometer speed selector device 3 which receives the speed-representing input on lead B. Operation in the "above" mode. The detection of a vehicle travelling at above the predetermined speed causes the speed selector 3 to produce a positive output on lead C, thereby actuating a squaring amplifier 4, which is enabled for operation by the actuation of a monostable multivibrator 1 by a vehicle presence pulse on the lead A. The squaring amplifier 4 produces outputs on leads D and E,the output on the lead D being passed via the operation selector 20 to an electronic counter 9, Fig. 2a, and the output on the lead E inhibiting a circuit 14 from producing a reset pulse on a lead G, such a pulse being produced to reset the counter 9 when and only when a vehicle travelling at below the predetermined speed is detected. A selector switch 10 may be adjusted to any of the values 1-4 to produce an output on a lead M when a corresponding value has been reached in the counter 9. An output on the lead M is effective via closed contacts of a relay 13 to energize a relay 12 which is unclamped by a signal on a lead Y produced as a result of the operation of the squaring amplifier 4. The energization of the relay 12 de-energizes the relay 13 to apply A.C. on a lead V to a remote alarm 15 via contact d of a switch SW3. If the switch SW3 is in position c, however, the passage of each subsequent vehicle is effective, via leads R and W to cause pulsed operation of the remote alarm. If a subsequent vehicle speed is detected which is below the predetermined speed, a signal on the lead K is effective to reset the counter 9, and via a switch SW1, to energize the relay 13 thereby resetting the alarm circuits. The switches SW1, SW3 and a further switch SW2 are ganged together, the closed position of switch SW1 corresponding to positions a, b, and c of switch SW3. If switch SW1 is open, the counter 9 is reset without reset of the alarm circuits which, however, may be reset by a remote button 101 which also resets the counter 9 via a diode D1 or the switch SW1. The switch SW2 is closed when SW3 is in position a, and is effective as a local reset switch. Operation in the "below" mode. Detection of a vehicle moving at a speed below the predetermined speed causes the multivibrator 1 to produce a pulse on a lead F and since the squaring amplifier 4 is not actuated, the circuit 14 is not inhibited and produces an output on the lead G which, since the selector 20 is in the "below" position, is effective to actuate the counter 9. The counter 9 is reset on the detection of a vehicle travelling at above the predetermined speed. The operation of the alarm and resetting circuits is as described above. Electronic counter. The counter 9, Fig. 2a, comprises two bi-stable tube flip-flop circuits and has lamps for indicating values 0-3. The selector switch 10 enables the required predetermined count to be selected. Additional indicating arrangements. A "vehicle pulse indicator" lamp, Fig. 2a, is connected to the output of the multivibrator 1 and is illuminated by the passage of each vehicle. A "critical speed indicator" lamp, Fig. 2a, is connected to the output of the squaring amplifier 4 and is illuminated momentarily whenever a vehicle is detected above the predetermined speed in the "above" mode, and is illuminated continuously when any speed below the predetermined speed is detected in the "below" mode.