Patent GB-362088-A (GB)
Title: Improvements relating to automatic telephone systems
IPC: H04Q3/00
Filed: 1930-10-15
Abstract: 362.088. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, and CHRISTIAN, D. A., Morven, Charlton Road, Charlton, both in London. Oct. 15, 1930, No. 30782. [Class 40 (iv).] A numerical selecting stage comprises two ranks of single motion switches, the first of which connects with a link and the second with an outlet, both of which are selected by a common controller which also comprises the operating relays. The outlets from the second rank of switches are graded and the system is arranged so that the second rank switch having access to an early choice graded outlet in a required direction is selected in preference to a switch having a later choice outlet. A switch having an early choice outlet in one direction has different choice outlets in all other directions and its order of test is dependent on the outlet direction required. The last choice outlet may lead to a switch, common to a number of last choice terminals, which has access to a number of auxiliary junctions. When a call arrives a first rank switch 1stR (Fig. 1) is selected and the controller CC is seized. The routing digit steps wipers WB to the required level and then wipers WR and WB step round together to find a free switch 2ndR having a free outlet L6. When this is found the selected 2ndR switch hunts for the selected outlet and the seized 1st R switch hunts for the marked link. If a final choice outlet is seized one of the switches MS hunts for a free auxiliary line. The outlets from 2ndR are graded as shown and the connections of other outlets to the switches are such that switches 1 and 2 having individual outlets on terminal 6 would have lower choice outlets on other terminals whilst switch 10, which has the final choice outlet on terminal 6 would have an individual choice in another direction. WR may be bi-directional and in this case the 2ndR switches are wired to its various levels in the same order as the outlets from 2ndR are graded so that a switch having an individual choice in a certain direction is tested, when a call is being routed in that direction, in priority to switches having lower graded outlets. The circuit arrangement is indicated in Fig. 2. When a call arrives N operates followed by Q, A, and S. D pulls up and V responds to the digit train stepping WB to the required level. When the train ceases, D releases and wipers WR and WB move round. When WR2 finds a free link TD (I) is energized, when WB3 finds a free outlet TD (II) is energized and when both these windings energize together TD operates to stop rotation. The seized switch 1stR is then rotated by 1stD to find the link marked over WR3 when TA pulls up- At the same time magnet 2ndD of the selected switch 2ndR is operated over WR1 and when this switch finds the outlet marked by WB4, TB pulls up. If a final choice has been selected, MD is operated and MS hunts to find a free outlet, such as T6, marked by battery which operates TC (1). TC locks over TC (II). Choices other than the last are connected to battery over WB1 to operate TO. With TA, TB and TC operated, P energizes, locks to the test wire, and switches the circuits through. N releases followed by Q, A and S, Z pulls up to release the controller and all operated relays therein de-energize. To prevent crossed connections being made when more than one controller is marking simultaneously switch 2ndR is provided with a bank 5 individual to each controller. The auxiliary outlets served by MS may be a separate group of circuits or may be multipled to outlets in the main group.