| 摘要 |
1,003,773. Automatic exchange systems. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. Dec. 27, 1962 [Dec. 29, 1961], No. 48643/62. Heading H4K. In a switching network comprising at least two cross-point switching stages, means connected to the links between the stages enables the free, busy or just-marked condition of the links to be detected. The system uses PNPN transistors in the switching stages and the trunking arrangements are similar to those described in Specification 849,873. In setting up a call, a common marker marks the inlet and outlet of the network and also successively marks each of the cross-points in the selected channel between the inlet and outlet and a checking device which is connected to every link of the network determines at each step of the switching operation that the just-marked cross-point and only that cross-point has operated. As shown (Fig. 7) each of the links extending from the A-frame to a particular switching matrix of the B-frame (as indicated by the co-ordinate k=1,2,3,4) is connected by a common wire to a checking unit 35 (Fig. 10). Each of these wires 76 to 79 passes through a magnetic core 71 to 74 each of which has been set to one magnetic state at time t6 of a preceding pulse cycle. At time t2 one of the pulse generators 81 to 84, e.g. 82 (k = 2) is set whereby at time t4 it can be fired by a pulse from clock 91. The selected cross-point is fired at time t3 of the cycle and so generates a pulse on one of the links in the set with k = 2 which pulse is effective in triggering over the associated core, e.g. 72. Consequently pulse generator 82 at time t4 resets core 72 and a pulse is produced in output pulse generator 95. In the event that a link of another set (e.g. k=3) is marked a further core 73 is triggered over at time t3 whereby a fault indication is given by output generator 95 when the cores are all reset at time t6. A system using two cores operating as an amplitude discriminator for each set of links is also described (Fig. 9, not shown) whereby the marking of more than one link of a set can be detected. A cross-point which has broken down prematurely can be detected by observing the condition of cores 71 to 74 before they are subjected to a pulse at time t3, i.e. before a crosspoint is fired from the marker. In another arrangement which merely checks that at least one link has been marked all the links between two stages are connected to a common checking device (Fig. 6, not shown). The generators 81 to 84 and 95 comprise saturable cores and transistors (Fig. 8, not shown) and are of the type described in Specification 917,119. |
