| 摘要 |
989,892. Fouling protection. STANDARD TELEPHONES & CABLES Ltd. Jan. 11, 1962 [Jan. 12, 1961], No. 1082/62. Heading B7N. In a fouling protection arrangement for a railway signalling system in which the layout of the signalling circuits corresponds to the layout of the track elements, a static fouling protection circuit setting element, e.g. a transistor or transductor, is provided in each electrical link corresponding to the track leading to each track element and one terminal of the fouling protection search signal source is connected to the junction of the setting elements associated with each track element. If fouling protection is sought from the direction 1 in the layout shown in Fig. 4, a negative voltage appears at input terminal e1, since the illustrated points cannot provide protection for this condition the search is extended in the directions 2 and 3 by the transistor circuit shown which when terminal e1 is negative produces a negative voltage at output terminals a2, a3. A search signal arriving at terminal a3 requesting protection from the direction 3 switches the voltage at FSR from negative to positive whereby the points are set to their right hand position to provide the necessary protection. Similarly the points are set to the left when a search signal arrives at terminal e2 from direction 2. |
