GB1219123A - Improvements relating to toll systems for road vehicles - Google Patents

Abstract

1,219,123. Toll system for road vehicles FERRANTI Ltd. 15 Jan., 1969 [17 Jan. 1968], No. 2452/68. Headings G4T and G4Q' A toll system for road vehicles comprises a toll point for each vehicle lane, there being a sensor 11 in the road which, on passage of a vehicle causes an interrogator station to emit a signal, which signal is received by transponder (Fig. 2) on the vehicle, debits a prepaid credit unit, and sends a reply signal to the interrogator. If the vehicle has no credit or no transponder, no reply signal is sent and a cine camera 27 is actuated which records the rear number-plate. The sensor utilizes pressure, photo-electric or magneto-electric sensing and the signal may be radio, infra-red or photoelectrical. The passage of the front wheels of a vehicle over pad 11 emits a pulse which causes gate generator 12 to generate a gating pulse, e.g. of 25 ms., and which also activates transmitter 13 to emit a signal at frequency f1 through antenna 15 and also activates receiver 16. If the vehicle has a transponder, the signal is received by receiver 42 and passed through modulator 44 and AND gate 45. The other input of the AND gate is connected to a credit store (pulse counter) 51 which only emits a signal if the store has credit. It is intended that this credit store be officially credited at some chosen time interval and is secured in the transponder by lockable leads. If the vehicle has credit, one or more units are debited from the store and transmitter 46 sends the reply signal at frequency f2 which is received by receiver 16. The interrogator includes a logic network 21 including a 2-stage binary counter 22, an inhibit gate 23 and AND gates 25, 26, gate 26 being opened when the counter holds number 3 (i.e. 2<SP>0</SP>+2<SP>1</SP>=3). Counter 22 normally holds 1, the gating pulse from 12 sets it to 2, but a signal received from receiver 16 resets the counter and returns it to zero. The rear wheels of the vehicle (which have no transponder) set the counter back to 1. If, however, the vehicle emits no reply signal (i.e. no credit or transponder) the rear axle wheels set the counter to 3, gate 25 opens and camera 27 is fired for a few seconds to record the numberplate. Gate 26 opening, inhibits gate 23 and thus keeps the counter at 3 until receiver 16 again receives a signal. Thus the next vehicle which appears will activate the camera regardless of whether it is in credit or not. This waste of film may be prevented by a modification (Fig. 5, not shown) which resets the counter after each camera operation by means of a differentiator and a buffer stage. In an alternative embodiment the signals f1 and f2 are the same frequency in which case a delay circuit is provided for the receiver 16. A higher rate may be set for peak periods by installng a second interrogator station which only operates during these periods. In an alternative credit store, the credit may be added instead of subtracted.