Patent GB-542176-A (GB)
Title: Improvements in or relating to telecommunication exchange systems
IPC: H04M3/523
Filed: 1940-06-28
Abstract: 542,176. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd., WRIGHT, E. P. G., HARTLEY, G. C., and STOKES, H. R. June 28, 1940, No. 11004. [Class 40 (iv)] In a system for presenting waiting calls to automatic or manual switching equipment in the order in which they were made, apparatus responsive to the arrival of a call when (say) the two previous calls have not been answered, ascertains the number of the calling ing line with the help of a callfinder LF, Fig. 1, and registers the number on one of a number of condenser registers connected up in turn by a switch CS. As switching equipment becomes available the registers are connected up in the same order by a switch DS to control the presentation of the waiting calls to the switching equipment in the order in which they came in. In the arrangement shown, in which the calls are answered manually, the record is used to light the appropriate calling lamp. Storing calls.-When two calls are already awaiting attention, the operation of an additional line relay L, Fig. 2, increases the current through the left-hand winding of a relay QS in the common equipment sufficiently to cause its operation. In consequence relay CL which normally lights the calling lamp is unable to operate and QSR energizes ST to start the finder LF in search of the calling line in known manner under control of LT. On the operation of the latter, relays LH, LHR, Fig. 3, and LL, Fig. 2, are operated and normally-energized relay D is released. As a result a temporary circuit is made via wipers lfc, lfd for a relay in each of two groups GA ... GJ and RA ... RJ, Fig. 3, to register two digits characteristic of the calling line, and a corresponding record is made on two groups of four condensers reached over wipers csa ... csh. At the same time LT is released to energize the driving magnet CSM of switch CS and when LH is unlocked shortly after the relapse of D the switch CS makes a step, the relays GA... RJ are released and the next condenser register is discharged. Distributing calls.-When one of the two calls previously awaiting attention is answered, the corresponding relay CL falls and the resulting reduction in the current in the left hand winding of CR causes its operation, whereupon RR, DR, Fig. 4, are operated and a sluggish relay R Z begins to release. The first digit of the line at the head of the queue is thus transferred from the condenser register to a group of relays A ... D via the upper set of wipers of switch DS. The operated relays lock temporarily in series with corresponding relays of a tens register TA ... TD which lock up in series with a relay TP and shunt out the relays A ... D. TP energizes CO which switches over to the lower set of wipers of DS whereupon setting of the units condenser register is transferred to the test group A ... D and then to a units relay register UA ... UD, the operated relays of which lock in series with UP. Relays DR, RR are released but a holding curcuit is made to prevent the release of RZ. On the relapse of RR or, if the number is not registered owing to a fault and RZ falls back, the switch DS is stepped on. The setting of the tens register TA ... TD is transferred to a ten-relay register DA ... DJ and the units register relays UA ... UD themselves apply ground to the appropriate one of ten bus-bars A ... J. A circuit is thus made for the middle winding of the relay CL of the line at the head of the queue and the relay locks up and lights the calling lamp. If the registration of a call is faulty and no circuit is made for the middle winding of CL, it is operated nevertheless after a delay by its left-hand section which controls contacts cl2 by thermal means.