Patent GB-309711-A (GB)
IPC: H04Q3/00
Abstract: 309,711. Relay Automatic Telephone Co., Ltd., and Johnson. B. B. March 21. 1928. Auto -In order to make the size of the selecting apparatus independdent of the number of external destinations, all outgoing and special service calls are arranged to leave the 1st selecting stage apparatus in the same direction, and to be separated in a group of 2nd stage apparatus which is available to all calling lines and incoming junctions or to several divisio switch to a relay office one of the divisions ot which is shown group over one of the links BO1 common to the bay of 5 groups, and a first choice trunk ot if there are any available to the bay, and a register marker R5 in group of trunks such as dt1 going to the wanted division, or the group jdt01 over which all outgoing calls are extended. The calling trunk and an idle one of the selected group are connected over a link in one of the bundles otl1 &c. a square symbol representing the arrangement of relays shown at a, Fig. 2, and a sloping line the arrangement shown at b. If the call is local, a registermarker RF in response to the remaining 3 digits causes the wanted line to be connected over a link B1 and a first choice trunk it if there are any available to a trunk IT and thence via links ITL, DT.L to the calling trunk. A trunk IT is not available unless it bas access to an idle link 1TL which has access to an idle link DTL connectible to the calling trunk dt1. More than one of the bundles DT may go to the same division. If the call is non-local, a register marker R7 in response to one or more further digits selects the group of junctions e.g. ojA7 leading to the wanted office and the call is extended to an idle one over links JTL, JDL. Calls arriving over the incoming junctions IJ are routed by register markers R6 either to the wanted numerical division or over trunks dj Oi similar to the trunks JDTO to the outgoing 2nd stage apparatus. Frames dfo, dfi are employed for connecting the bay trunks ot, it to the bundles OT, IT, in accordance with traflic requirements. Similar frames are provided at dfd, Fig. 5, dfo, Fig. 7, dfi, Fig. 6, and dfOJ, Fig. 7. The distribution at the last mentioned frame is shown in Fig. 8, which shows one or more junctions to each of the offices A - - J going to each of the bundles jt1 - - jt6. A and B feed and 1st stage recorder. Assuming the first link to be available, the operation of line relay LE1 and relay OTT1 energizes LM1 in series with 1L/10T, T, and thermostat Tt. LM1 energizes 1S/1L and A2, G, GX, N'D, BB pull up. GX holds the connecting relays in series with the busying relay LB1 and cut-off relay C01 which energizes F1. T over h energizes FI, Fig. 14, which, if the first register marker is idle, energizes RC1 which over p energizes P, Fig. 33, to prepare the counting relays MK, BK, and energize RSR1, RSR2. DM1 pulls up and locks itself and energizes MK1. FI locks over the wires a, b in parallel until the first impulse is received and then extends them over a1, b1 to the impulse wire i and over h1 energizes busying relay BY. At the end of the digit, DC1 which is connected to the wires a1, b1 by DC2 energizes one of the relays DH which energizes RH. RH connects battery to the impulse wire to prevent any alteration in the setting by the calling party, and energizes MC which , causes the relapse of RSR1, RSR2 and while they are falling marks the calling trunk over m and the wanted trunk group over one winding of SU and one of the wires ma, and energizes the other winding of SU. SU does not pull up unless a spare number is dialled. When it does, b being disconnected, and grounded, the differencial relay IS, Fig. 13, energizes ICO, and NU sends back NU tone. If the digit dialled is 7, DH7 releases DM1 which restores the counting chain whereupon DM2 pulls up and the recorder is ready for a second digit. Extension of call to numerical division. The marker energizes OTM1, Fig. 15, of the calling trunk and DD1, Fig. 18, of the wanted group. OTM1 energizes relays OLM of the idle links and DD1 energizes G-S1 over front contacts of the relays OLM. If the group associated with DD1 were busy and the adjacent group led in the same direction, DD1 would energize GJS. GS1 energizes SS which energizes (say) DTM1 of the first idle trunk in series with connecting relays 10tl/1dt and 1ot/1otl, which lock up in series with busying relays DTB1, OLB1, and RCO which releases the register marker. Extension of call to wanted line. The division trunks are associated through the connection shown in Fig. 19 with apparatus such as that shown in Fig. 14 which seizes a recorder similar to that described above but modified to respond to 3 digits. If the line is busy, a differential relay in the marking circuit similar to SU, Fig. 33, connects battery to the wire b and since the relay corresponding to RH has already grounded wire a, IS, Fig. 13, is unbalanced and energizes ICO. BB holds and LO sends back busy tone. If the line is idle, the marker energizes its line - relay (say) LEOOO in series with D and at the same time energizes OTM21, Fig. 21, of the calling trunk. OTM21 energizes the relays OLM21 of the idle links. LE000 energizes ITT1 which connects the test relays LM1, LM2 to the wires t. Assuming the upper trunk in Fig. 25 is jumpered to it1, Fig. 11, and is free, a circuit now exists for LM1, 1L/1IT, ITM1 over front contacts of the relays OLM. LM1 energizes OOOS/IL, and SS24 (energized by ITMl) energizes the relay (say) ILM1 of the first available link. A circuit now exists for the connecting relays 1dt/1dtl, 1dtl/3itl, 1ITL/1IT which lock up in series with the respective busying relays, RCO for freeing the register marker, the connecting relays OOOS/1L, 1L/1IT, and cut off relay CO.000 which energizes F.000 to release D, ITT1, LM1. RG in the trunk IT is energized by ITM1 and locks up, and on the relapse of ITM1 ringing current goes out over RT which cuts off RG when the called party replies.RG on pulling up disconnects the a-wire and grounds the b-wire. 1S is unbalanced and energizes 100 which locks up, cuts off IS and releases BB. B2 pulls up over the b-wire and releases ND which prevents the operation of NU. The reply signal energizes. B1 which energizes ME. Release, normal and forced. When the calling party hangs up, A2, G, GX fall back and release the connecting relays on the called side. rme is short-circuited and R which is not accurately balanced releases ME to free the calling side. If the called party hangs up first B1, B2 fall and connect up the thermostat Tt which after an interval short-circuits GX to break down the connection. If either party fails to clear, his line relay LE re-energizes and holds his relay F to prevent the initiation of a new call and mark him busy. Outgoing calls. The first stage marker energizes relay DJM, Fig. 18 (the dotted connection being omitted) when the special first digit for outgoing and special service calls is dialled, and the connection is extended to one of the trunks dt2 as described above. This trunk over circuits such as those shown in Figs. 19, 14, takes into use a register-marker which in response to one or more further digits operates in the same way as that shown in Figs. 33 - - 35 to mark the wanted group by energizing its relay OJM. Fig. 32, and the calling trunk by energizing OTM27, Fig. 27, which energizes the relays OLM27 of idle links. OJM energizes (say) OJS1 of the first idle junction over JTM1 and front contacts of redays OLM27. SS30, energized by JTM1 energizes (say) JLM1 of the first idle link whereupon the connecting relays 3jtl/jt, 1jdl/3jtl, 1dt/jdl pull up and lock in series with the busying relays JTB1, JLB1, OLB27 and RCO which releases the register marker.