GB862870A - Improvements relating to information transmission systems - Google Patents

Abstract

862,870. Electric selective signalling systems. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Jan. 24, 1958 [Feb. 5, 1957], No. 3936/57. Drawings to Specification. Class 40 (1). In an electric selective signalling system for signalling the angular position of a shaft from a field station to a central station an electric signal is produced at the field station having a frequency representing the angular position of the shaft (this being effected by a binary coded disc which selectively energizes in combination a number of relays whose contacts control the capacitance in the tank circuit of a triode amplifier) which signal is then transmitted by land line or radio to the central station where the number of oscillations that occur within a particular time period (approximately one-third of a second) are counted by a multi-cathode gas tube counter, whose cathodes, via a diode recoding network and some transistor amplifiers, control a storage and indicating device such as described in Specification 721,683, which is referred to. In a further embodiment in which the field station includes a plurality of shafts all of whose angular positions have to be transmitted to the central station a uni-selector switch is interposed at the field station between the several shafts and the oscillator and a second uni-selector synchronized with the first is interposed, at the central station, between the output of the diode re-coding network and a plurality of indicating devices corresponding to the plurality of shafts at the field station. In another embodiment the plurality of the shafts are each at a separate field station, each field station having a uni-selector switch synchronized with that at the central station, and the field stations transmit their signals in succession.