Patent GB-717996-A (GB)
Title: Improvements in or relating to circuits for use in automatic signalling systems
IPC: C09D7/12
Filed: 1952-08-01
Abstract: 717,996. Automatic exchange systems. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Aug. 1, 1952, [Aug. 4, 1951], No. 19523/52. Class 40 (4). A register controls a first group selector to gain access directly to a desired outlet of a second group selector. If such direct connection is not free, the register controls the first and second group selectors in turn in normal manner. By this system considerable economy is effected in second group selectors. The invention is illustrated schematically in Fig. 2 as applied to an exchange of .more than 1,000 lines. When the first two digits have been stored, the register RG knows to which group of 100 subscribers, say AB1, the called subscriber belongs, and so via which group of final selectors EK11-13 the connection is to be made. The register tests to see if one of the group, say EK11, connected directly to first group selectors GK11 is free, and, if so, GK11 and EK11 are adjusted to the outlet desired, the group selector GK11 being adjusted in accordance with two digits. If no direct connection is free, the first group selector GK11 is adjusted by the first digit to a second group selector GK2, which is then adjusted by the second digit to seize a final selector EK in normal manner. In an exchange for 9,000 subscribers, the first group selectors GK1 may have two sets of wipers each with 100 outlets, the register determining whether a direct connection can be obtained to the final selector over the one set of wipers or an indirect connection shall be made over the other set of wipers. This system is shown in detail in Fig. 3. The four digits of the called number are set up on switches MD, MH, MT, ME in the register, the outlet contacts being marked with voltages representative of the digits. When the units digit is set up contacts me reverse and as tube B and relay T are normally energized, rotary magnet DG drives the first group selector GK1 in search of a directly connected final selector EK of the desired group, H pulling up at the same time. A voltage comparison device NW 1 compares the thousands digit voltage supplied from VD1 to contact cl in GK1 with that on the marking switch MD, while another comparison device NW2 compares the hundreds digit voltage supplied from VH to contact d1 with that on switch MH. If a directlyconnected final selector EK of the desired group is free, NW1 and NW2 respond simultaneously and T falls back to stop the group selector GK1, release H, and energize HG. HG earths wiper d1 to mark the outlet busy, re-energizing T and M. M connects the voltage comparison devices NW1, NW2 to the tens and units marking switches MT, ME. Rotary magnet DE then drives the final selector in a circuit energizing Hand S. The tens marking voltage VT is returned over contact c4 and the b wire, while the units voltage VE is returned over d4 and the c wire. When the, desired line is found, NW1 and NW2 respond T, DE, H and S relapse. HE then energizes and the selection path is complete. If, however, the direct connection from GK1 is busy, NW1 and NW2 do not respond and GK1 continues to hunt until time-relay F falls back to operate P, O, and OG, the last releasing P and switching over the inlets of the first group selector GK1 from one set of wipers to the other. Relay O renders NW1 inoperative and connects the thousands marking switch MD to NW2. The group selector GK1 is adjusted under the control of NW2 and voltage VD2. When a free GK2 is found, T and H release and HG operates as previously described. After T re-energizes, N pulls up to connect the hundreds switch MH to NW2 and GK2 is adjusted until the desired voltage VH is found, when HK pulls up and T and H relapse again to energize Q. T re-energizes to the busy marking to operate M, which connects the tens and units marking switches MT, ME to NW1, NW2 respectively. H and S are now energized in series with magnet DE to drive the final selector EK until NW1, NW2 respond to the desired voltages on VT, VE, when HE pulls up and the selection is complete. In a larger system, Fig. 4, the first group selectors GK1 have access to the final selectors EK, the second group selectors GK2 or to other exchanges L1. Lines from other exchanges have access to the second selectors GK2, which have access either to the final selectors or to the third selectors GK3. In the line-finder system of Fig. 5, a call detector OD common to a group of 100 subscribers identifies the calling subscriber and transmits the number to the register which then connects the connecting circuit VCA or VCB to the line numerically by one, two or three stages. The register can also use switches OZ-GK and OZ-EK for connecting a connecting circuit to a called line, so that these switches can act either as linefinder or as numerical selector.