GB884720A - Coin-controlled apparatus - Google Patents

Abstract

884,720. Locating conductive bodies. FISHER, L. J. March 4, 1960, No. 7856/60. Class 37. [Also in Groups XVIII and XXXIX] In apparatus for signalling the values of coins deposited in the shoot of a telephone call-box, the shoot 6 has electromagnets 1 to 4 arranged along one side thereof, which are energized by the alternating voltage source 5 so as to induce voltages into pick-up coils 12 wound on cores 8 to 11 mounted opposite the respective electromagnets. The coils 12 on cores 8, 9 are connected in series opposition with those on cores 10, 11 so that normally no voltage is applied to the pulse generator 15. Coins of different values are inserted at different points in the shoot 6 via slots (not shown), such that a coin passes different numbers of electromagnets 1 to 4 in accordance with its value. As a coin, which may be metallic or non-metallic, passes an electromagnet the resulting change in the voltage induced in the corresponding pick-up coil gives rise to a voltage at the input of generator 15, so that a number of pulses is generated which corresponds to the value of the coin. Each electromagnet and each pick-up coil may be replaced by an electrode, each such pair of electrodes forming a condenser. Embodiment using transistors, Fig. 4.-The four coils g1 to g4 of electromagnets 1 to 4 are connected in series in the collector circuit of transistor T1 together with the tuning condenser C1, and associated feed-back coils g<SP>1</SP> 1 to g<SP>1</SP> 4 are connected in the base circuit. When battery is connected to this oscillator by the telephone subscriber taking down his handset, it oscillates at a high audio frequency. The pick-up coils are connected at m1, m2, m3, m4 in the base-emitter circuit of transistor T2 and in the normal condition produce no output. When a coin passes down the shoot, each pulse of alternating voltage produced in the baseemitter circuit of T2 causes that transistor to conduct. The resulting potential drop in R3 causes T3 to conduct also, so that the leg L2 of the telephone line receives one or more ground pulses in dependence upon the value of the coin.