Patent GB-361519-A (GB)
Title: Improvements in electromagnetic switches as used in telephone or like systems
IPC: H04Q3/00
Filed: 1930-10-08
Abstract: 361,519. Automatic exchange switches and systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, and CHRISTIAN, D. A., Morven, Charlton Road, Charlton, both in London. Oct. 8, 1.930, No. 30163. [Class 40 (iv).] A single drive rotary switch is provided with two wiper sets, one wiper set connecting with inlets and the other with outlets, and is arranged so that in one complete cycle each of the inlet terminals is connected with each of the outlet terminals. The use of such switches as group selectors in a bypath system is described. As shown in Figs. 1 and 2, two ratchet wheels 13, 14, of different size and having a different number of teeth, are operated by pawls 9, 10 connected together and to armature 6 of electromagnet 5. Ten contacts are, for example, provided on the bank associated with ratchet 14 and eleven with that associated with ratchet 13, the eleventh contact being spare. The wipers are arranged so that as one tip leaves a contact bank another tip enters it, and, as both ratchets are stepped together, it follows that one wiper lags behind one step for each complete traverse of the banks and after ten complete traverses, forming a cycle, each contact in one back has been associated with each contact in the other. Instead of making the two ratchets of different sizes, ratchets of the same size can be used provided with teeth of different pitch, lost motion being provided on the pawl of one of the ratchets. Alternately one wiper set can be arranged to move one step for each complete traverse of the other wiper set. Fig. 6 illustrates the use of these switches as couplers in a bypath system, first and second couplers FC and SC, both of this type being provided. The preceding switch tests for absence of earth on c and when this is found earth is connected to p to energize T, operating X and connecting A to the b wire. The impulse train is transmitted from the register controller and A responds, repeating the impulses to VM to step control switch CS. D operates on the first impulse and holds during the train, but when the series ceases, D releases and RM steps the wipers of CS in search of a free first coupler, denoted by earth on wiper 1, and a free second coupler denoted by absence of earth over wiper 2. Relay GP is common to a group of links and is provided to prevent more than one link in a group being marked for use at the same time. Assuming couplers FC and SC are found free and available, TC operates opening the circuit of RM and completing a circuit over wiper 3 for RF and GP in series. RF completes a circuit for DFM which starts FC hunting for the calling circuit, denoted by earth on e and for a free outlet to SC, denoted by absence of earth on r. When these conditions are complied with TF operates and switches through. TF also connects earth to wiper 5 of CS to operate EF which enables RS to pull up. RS completes a circuit for DSM of the second coupler SC and this switch hunts for the calling link, marked by an earth on d and for a free outlet, marked by absence of earth on r, and when these conditions are found TS operates and switches through. Relay ES operates over 6 of CS and K pulls up over its winding (1) and locks over its winding (II) to the incoming p wire. T, X, and A release, relay T removing battery from the a wire to allow the next digit to be transmitted. Relays TC and TD fall away and ZM operates to release the control switch. EF, ES, RF, RS, and GP fall away. The connection is released by the removal of earth from the c wire, releasing TF, TS, and by the consequential removal of earth from the p wire releasing K. In an alternative arrangement the control switch CS also searches for a free link LC, the two couplers then searching simultaneously for the marked link. The links may be preselected and allocated for use in turn by a distributer.