GB1022534A - Vehicle detectors - Google Patents

Abstract

1,022,534. Road traffic measurements. LABORATORY FOR ELECTRONICS Inc. Oct. 9, 1962 [Oct. 9, 1961], No. 38259/62. Heading G4Q. [Also in Divisions B7, H1 and H4] The passage of a road or rail vehicle is detected by mechanical displacement of part of an active semi-conductor device so that the conductivity of the device is altered. In one arrangement, Fig. 1 (not shown), a point contact transistor is mounted within a housing mounted under a road and may be hermetically sealed within the housing by a solid, liquid, or gas insulating medium. The transistor is biased either to conduct or not to conduct, and vibrations transmitted to the transistor cause it to reverse its conductivity state. A diode may be included in the circuit so that the output comprises pulses of only one polarity. In modifications, Figs. 2 and 3 (not shown), the transistor is of the junction type, and in a further modification, Fig. 5 (not shown), a piezo-electric crystal 56 is mounted above the base of a junction type transistor. In other arrangement, Fig. 4 (not shown), a road treadle 40 is connected to a point contact emitter electrode 42 such as a stiff tungsten or phosphor-bronze wire; movement of the treadle moves the point contact across the surface of the base of a transistor and thereby alters its conductivity. In a modification, Fig. 4 (not shown), the base of a transistor is provided with spaced conductive coatings, and vehicle actuation causes an emitter to rotate from contact with one conductive area 49<SP>1</SP> to contact with a second conductive area 49<SP>11</SP>