INPUT CIRCUIT FOR A SIGNALLING SYSTEM WHICH CYCLICALLY SCANS A PLURALITY OF SIGNALLING STATIONS UNDER COUNTER CONTROL

摘要

Each of a plurality of changeover switches is provided at a corresponding one of a plurality of signalling stations and has a first contact terminal connected to the positive polarity terminal of a DC voltage source and a second contact terminal connected to the negative polarity terminal of the DC voltage source. Each of the plurality of transistor circuits is provided at a corresponding one of the signalling stations. Each transistor circuit comprises a PNP type transistor and an NPN type transistor connected in parallel with each other and connected to the fixed terminal of the switch arm of the corresponding one of the changeover switches. Each transistor circuit is electrically connected to a bus bar for applying a potential between the potentials of the terminals of the DC voltage source via the control winding of the corresponding one of the magnetic cores. Each transistor of each transistor circuit has a base electrode coupled to a counter via a decoder. The counter is controlled by a pulse generator.