Patent GB-801960-A (GB)
Title: Improvements relating to automatic telephone exchange systems and the like
Inventor: FLOOD JOHN EDWARD
IPC: H04Q3/42
Filed: 1956-01-24
Abstract: 801,960. Automatic exchange systems. SIEMENS EDISON SWAN, Ltd. Jan. 24, 1957 [Jan. 24, 1956], No. 2324/56. Class 40 (4). A translator, comprising a storage device such as a magnetic drum, receives code digits and uses a lesser number of these digits to select on a main track of the storage device an address at which translation information corresponding to said lesser number of digits is stored in serial form, said information including a distinctive characteristic if the lesser number of digits are such as may belong to a code requiring translation for a greater number of digits, means responsive to the reading of such distinctive characteristic causing the selection of an auxiliary track bearing translations in respect of said greater number of digits. The systems described are modifications of those described in Specification 805,326. First embodiment, Figs. 1, 1a. Areas of an exchange system are identified by three code digits and exchanges within each area by a further three code digits. For local calls only three digits are dialled. For toll calls up to 6 digits are dialled. The code digits identifying an exchange are received by a translator from a register over six groups of leads L1-L6 in a two-out-of-five code and, as described in the earlier Specification, energizes one out of ten relays in each of six groups RA-RF. The selected relays RA, RB select the reading head MH associated with one of 100 main tracks on a magnetic drum. Relay RC controls gate G2 to pass the information on one sector of the selected track, this information comprising first and second choice translations as shown in the upper line of Fig. 1a. If the three code digits selecting an address on a main track represent an area for which a translation for six code digits are required an " instruction digit " is included in the first choice translation to indicate on which of ten auxiliary tracks such translation may be found. Gates-G3, G4 receive the digits stored in the selected main track address in respect of the first three code digits. When an instruction digit is read it passes through G4 to operate two of five trigger circuits T3 which inhibit gates GE1, GE2 to prevent the first and second choice translations on the main track being sent to the register. At the same time relay K pulls up. The operated trigger circuits T3 also operate a pair of associated relays RH to select one of ten reading heads HA associated with the auxiliary tracks. These tracks are divided into sectors each of which carries the second set of three code digits of a six-digit code followed by a seven-digit translation, Fig. 1a. At the next rotation of the drum the information on the auxiliary track is fed to gate G10 where it is compared with code digits D-F from the register. At coincidence gate G10 opens to step counter CR1 to sixth position. Gate G14 is therefore opened to pass the translation digits from the selected sector of the auxiliary track to gate G15. At the appropriate time in the cycle G15 sends the translation digits to trigger circuits such as T4 which inhibit gates G7 and G8 and mark the associated gates such as GE3 whereupon the first translation digit is sent to the register. The register applies afresh to the translator for each translation digit. If the route indicated by the auxiliary track :is busy the register requests the second choice and gate G18 stimulates the GE1 gates whereupon the first choice translation on the main track is taken as an alternative. The trigger circuits are reset at each rotation of the drum by cyclic binary counter CR2. Second embodiment, Figs. 2, 2a. Each area is identified by one digit and each exchange by 2, 3 or 4 additional digits. The instruction digit in the first translation on the main track now indicates whether the translation sought is one for a 4- or a 5-digit code. The code digits A-C select a main track as before. The instruction digit preceding the second choice translation, Fig. 2a, passes through gate G21 to operate one or other of two trigger circuits T5, T6. The B and C digits from the register additionally control relays such as RB<SP>1</SP>, RC<SP>1</SP> which combine with the selected relay RD, and where applicable RE, to apply a binary representation of the exchange code digits to gate G10 where they are compared with the several sets of code digits read from the auxiliary track. At coincidence counter CR1 steps 6 or 8 times as the case may be to open gate G26 or gate G28 whereupon the corresponding translation is fed to G15 as in Fig. 1. The registers may be connected cyclically to the translator, scanning of the registers being halted when operation of trigger T3 indicates that the auxiliary track is to be read. All trigger circuits are restored at the beginning of a new rotation of the drum. Test for busy routes, Fig. 8. The translations include digits other than routing digits. The routing digits may be abstracted separately and used to determine whether the route is idle or busy whereby an alternative route may be selected where necessary without delay. In this case the register does not mark the choice of translation leads L8, L9 but merely asks for the first translation digit by marking the appropriate L7 leads to open gate GG1, Fig. 8. If an auxiliary track is selected the translation digits are fed to G15 and G30, the latter passing them to G31 and G32. Assuming two basic routing digits they energize appropriate relays RM, RN which select the " route busy " wire for the route to which they relate. Similarly the first and second choice translations on the main track energize relays RO, RP and RQ, RS for selection of appropriate " route busy " wires. At the next rotation of the drum trigger T7 operates to stimulate gate G40. If the route selected by the auxiliary track is free gates G41, G42 open to mark the first choice lead L8 and the first translation digit is sent to the register. If, however, this route is busy G40 opens to mark the first choice busy lead L11. The first choice translation on the main track is then selected unless that route is also busy when G46 opens to mark lead L12. With leads L8 and L9 unmarked no translation is then sent to the register. If no auxiliary track is selected T7 remains normal. If then the route selected by the first translation on the main track is busy, relays RO, RP open gate G47 to mark lead L11. If the second route is also busy RQ, RS open gate G48 to mark lead L12 and no translation is sent to the register. Assuming that a free route has been found the register marks one or other lead L8 or L9. Gate GG1 is then inoperative and the translator operates as described with,reference to Fig. 1 or Fig. 2. Saturable transformers may be used to select a reading head in the manner described in Specification 805,326.