| 摘要 |
963,319. Automatic exchange systems. STANDARD TELEPHONES & CABLES Ltd. Oct. 19, 1962 [Oct. 25, 1961], No. 39656/62. Addition to 953,895. Heading H4K. In an arrangement comprising a plurality of cascaded cross-point matrices, in which marking of an input to the first of the matrices initiates a search over all paths extending towards outlets of the last matrix, one of which is marked, arrangements are provided to restrict the search only to those paths which can effect connection to the desired outlet. As shown, an interstage line such as 55 cannot be searched unless it is enabled by potential applied over a gate such as 68. In the case of an incoming call, connection between a line such as 10 and a preallotted link #1 is effected over a primary matrix 50 and an intermediate matrix 51. When a link is allotted, closure of contact 63 marks the link and contact 69 marks all primary-intermediate lines such as 55, capable of effecting connection to the link. The marking voltage applied to the incoming line is a voltage steadily rising from 0 to +18 v. The link marking voltage is -18 v. as is also the potential applied to the lower plates of condensers 79. Marking of a line such as 55 lowers its potential from a small value to -18 v. When an incoming line is marked, all the crosspoints D (which may be PNPN diodes) connecting it to marked lines such as 55 start to break down. The first to do so immediately raises the calling line side potential so that the others cannot fire at this time. Moreover; the rise in potential of line 55 then causes an intermediate cross-point D6 to fire to complete the connection to a link #1. The current thus flowing through the diodes holding them conducting. The potential on the line 55 then changes to between 0 and -4 v. which should be sufficient to prevent diodes connected thereto from firing. However, to prevent unwanted connections to a busy line in marginal conditions, guard circuits 105 are provided in which the condenser resistance combinations CR are connected to the line via PNPN diodes GD. Point JV is at -10v, so that if D fires and the potential of 55 rises, diode GD fires and condenser C charges. When C is charged diode GD losses current and cuts off. This now enables condenser 79 to charge up and so cut off D, whereupon other diodes connected to line 10 are permitted to fire provided they give access to paths marked by the link. When the wanted number is registered in the link (say 30), the multiple 95 is marked by means not shown and also enabling potential is applied to lead 89. This is applied via gates 84, 73, 90 to mark all possible paths back to the link. A search is made as before through these paths until one is completed back to the link, whereupon the connection is completed. |
