Patent GB-503147-A (GB)
Title: Improvements in or relating to telecommunication exchange systems
IPC: H04Q3/00
Filed: 1937-10-01
Abstract: 503,147. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd. (Hertog, M. D., and Kruithof, J.) Oct. 1, 1937, No. 26624. [Class 40 (iv)] In a system in which incoming junctions are extended to outgoing junctions in the wanted direction over primary and secondary. finders and in which all the idle primary finders of a group are started by the arrival of a call, the secondary finders hunt for the first idle primary finder of the calling group while the primary finders are hunting. The outgoing junctions in a particular direction are in two groups, high-quality junctions Y for longdistance calls and, lower-quality junctions X for calls to the neighbouring exchange, the former group serving also as an overflow group for the short-distance calls. If a call arriving over the junction ITL is for the X group of junctions in the direction shown, the marker M associated with the incoming junction is set to position x to mark the calling junction to the primary finders IF and energize the starting relays Fsri., Fsrx. Fsri energizes Isr which completes the circuits of the driving magnets IFM of all the idle primary finders serving the calling junction. Fsrx energizes Xpr which marks the calling primary group to the secondary finders of the X group by connecting battery over the relays Xpr1 .. Xpr(n) to such of the terminals 1 .. n as correspond to idle primary finders. Xpr also energizes Asrx which energizes the driving magnets OFMx of the idle secondary finders. When a secondary finder reaches the first idle primary finder of the calling group, its relay Otrx stops it and energizes Ohrx which renders the seized primary finder non-selectable to other secondary finders. At the same time, the relay (say) Xpr3 corresponding to this primary finder pulls up and energizes the next relay of the series. Xpr4 energizes Xpr5 and so on, and ground on terminals 4 .. n drives off any secondary finders that may be on these terminals. When one of the primary finders reaches the calling junction, the test relay 1tr stops it and energizes 1hr which energizes 1or, connects battery to the corresponding terminal 1 .. n over a resistance instead of over the corresponding relay Xprl ... Xpr(n), and energizes Hcrx. This releases Xpr, to.release the relays Xprl .. Xpr(n), and makes an alternative circuit for Asrx. Only the successful primary finder is now marked in the bank 1....n and if a secondary finder is standing on the marked terminal its relays Otrx, Ohrx remain operated. Otherwise, the hunt is resumed and in due course a finder is stopped by Otrx, and Ohrx shunts out the start relays Fsrx, Fsri and makes a circuit 'for Horx in series with Cwr and Cor. Cwr energizes Ier which causes the release of Itr, Ihr, Hcvx, Otrx, Ohrx. If the marker indicates group Y initially, Fsry is energized instead of Fsrx and Ofr additionally, and the call is then extended in a similar way by the second finders of group Y. If the X group is designated when it is completely busy, Abrx, which normally operates in series with the finder magnets when Asrx pulls up, is unable to operate and in consequence Sur pulls up and locks and energizes Ofr to cause the Y group to hunt.