Patent GB-416094-A (GB)
Title: Improvements in or relating to automatic or semi-automatic telephone or like exchange systems
IPC: H04Q3/42
Filed: 1933-03-13
Abstract: 416,094. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd., WRIGHT, E. P. G., and GOULD, J. R., Connaught House, Aldwych, London. March 13, 1933, No. 7563. [Class 40 (iv).] A first code selector finding no idle direct junction to the wanted exchange may take into use over the later terminals of the level a non-numerical switch which hunts for a junction in an alternative direction. A signal is sent back to the register-controller to hold up transmission of the numerical digits, while common apparatus is associated with the hunting switch to send the additional digits necessary to route the call to the wanted exchange. Upon seizure of the switch JH, relay L energizes over the loop, the current therein being reversed to prevent further impulsing from the registercontroller, and starts the hunting operation. Test relay K energizes on an idle junction and connects up ST to associate the common apparatus as soon as the sending switch TS is in the normal position. Relay 1G energizes when the impulse springs IS open, and connects them to SS, which repeats the impulses to step the switch TS. Each control bank is wired by means of strapped terminals to give a normal routing number comprising one, two or three digits, and the front contacts st3, 4 in each switch JH are connected to leads PU, CO wired to the appropriate bank. The switch TS may thus deliver simultaneously the appropriate routing digits to all the switches JH with which it is associated, these being repeated over the selected junction by relay A. Switching relay H operates when sending is complete and ST falls back. Current in the normal direction is fed back over the junction, and the numerical digits are sent from the register-controller. Two sets of common apparatus may be provided giving different sets of routing numbers, and each may serve as a reserve for the other, change-over keys COK 1, 2 being provided. Each control bank of the switch TS is therefore wired to give a reserve routing number which is that normally given by the other sending switch by means of strapped terminals in the spaces between the digits of the normal routing number. Each switch JH may have access to junctions in more than one alternative direction, with discriminating means for selecting the appropriate bank of the switch TS. Moreover each switch JH may be accessible from more than one level of the first code selector, in which case a signal dependent on the route of access determines the routing number to be sent out. Relay TM may be connected up by keys such as TMK to register the traffic over any desired group of junctions, while a meter associated with each switch JH is controlled over lead TRL. Instead of delaying the transmission of the numerical digits from the register-controller, these digits may be received on registers in the common apparatus and transmitted after the additional routing digits. According to the Provisional Specification, spare C.C.I. repeater and coder equipment may be modified to provide the alternative routing equipment.