Patent GB-317724-A (GB)
IPC: H04M11/06
Filed: 1929-08-15
Abstract: 317,724. Siemens & Halske Akt.-Ges. Aug. 20, 1928, [Convention date]. Void [Published under Sect. 91 of the Acts]. Addition to 306,406. Central station apparatus. - Comprises an automatic exchange system for telegraphy in which a call is effected as follows : the calling subscriber Tn closes an earth-return a to a preselector VW, individual to it, which hunts for a disengaged group selector GW. The subscriber then dials the first digit, and the group selector, being thus raised to the required level, hunts for a disengaged line selector LW. The subscriber then dials the second and third digits, so as first to raise and then to rotate the line selector LW. 'The call-up signal and message sinals are given bv reversals of the line current, a contactmaking relay E1 in the line selector serving to pass on these signals from calling subscriber to called subscriber. The line is cleared when the calling subscriber breaks circuit. Preselector VW individual to calling subscriber. When the calling subscriber Tn raises his switchhook the magnet R is energized via the upper contact HH1, and closes at R.9 the circuit of the rotary switching magnet D which, under the control of the interrupter Un, steps round the wipers a, b, c until the wiper c finds a disengaged contact, i.e. one which is earthed via contact J.17 and winding A.III of the group-selector : relays T of the preselector and A of the group selector are thus energzed via the above circuit and contact R.8. The relay T puts the leads a, b through at T.6, T.7 (thereby cutting in the winding A.I), cuts out the switching magnet D at T.5, cuts out the relay R and its balancing impedances at T.6, T.7, and holds on via the wiper d and contact T.5, the high-resistance winding T.II being momentarily short-circuited to protect the group selector from other calling subscribers. Group selector GW. The magnet T and winding A.I being thus energized, a short-circuit is, at A.15, applied to relay V but removed from relay C, which it had protected from premature energization. Relay C holds on at C.10. A dialling tone is thereupon sent back to the caller, winding J.II being cut in at A.3, C.4, so that the dialling tone transformer U1 has its secondary .circuit closed at J.17. The winding A.III serves as primary and the windings A.I, A.II as secondary for a further transformer for passing the tone to the caller's line a, b. The subscriber Tn on hearing the dialling-tone in his telephone Tl dials his first digit by closing the contact i repeatedly. Winding A.I is thus intermittently de-energized, the contact A.14 causing the lifting magnet H1 to operate the required number of times. Relay V is energized so as to disable the rotary switching magnet D1 at V..16 and relays C, V, being slow-release relays remain energized during dialling. The raising of the switch stops the dialling-tone by breaking contacts K.25 and K.1 and prepares a circuit for the rotary switching magnet D1 at K.26. When dialling stops, winding A.I remains energized by the line current and relay V is cut out at A.15, the circuit of the rotary switching magnet D1 being thereupon completed at V.16. The windings J.I, D1, and contacts J.18, D1.27, then cooperate to produce a cycle of interruptions so that the group selector GW rotates until its arm c finds a free line selector LW. Line selector LW. The arm c of group selector GW cuts in the windings P.I, P.II of the latter selector via contacts C.12 and K1.55. The lineselector windings A1.1, C1 are cut in by the wiper a and contact A1.31, respectively, while an alternative circuit for the relay P is closed at C1.33. Relay P halts the switch by breaking contact at P.19, holds on via P.22, and at P.23, 24 puts through the leads a, b, cutting out the winding A.I, A.II. At P.22 it shortcircuits the winding P.II so as to mark the groupselector " busy." The caller Tn then dials the second digit through his contact i, making and breaking the circuit of relay A1 so as to operate the lifting magnet H2 through contact A1.29. On the cessation of dialling the circuit of the rotary switching magnet D2 is prepared at U.49 by the winding U.I, whose circuit via C1:35 is closed at K1.53 by the lifting of the line-selector (but was interrupted, during the dialling of the second digit, by the slow-release relay V1 at V1.44). The resistance of U.I being high, the magnet H2 is not energized in this circuit. The caller then dials the third digit, intermittently energizing the relay A,. The slow-release relay V1 is energized via A.32 but the winding R.11 of the relay U now holds on via C,.34, U.48, V1.46, so that the circuit of rotary switching magnet D2, via P,.38 (normal) and U.49 (working) is intermittently interrupted at A129. The wipers a, b, c are thus stepped round to the desired line a1' b1, c1. Relay P1 operates (see below) and puts the leads a, b through at P1.40, 41. Marking the called subscriber " busy." At the conclusion of the third digit the relay A1 remains energized, relay V1 is cut out at A1.30, and relay U is cut out at V1.46 but releases only after a short interval. During this interval, when U holds but V1 is de-energized, relay P1 is cut in via C1.34, U.48, V1.46, test line T and battery at called preselector. Relay R of called station is cut off as at T.6, so that the preselector there cannot be operated. The line-selector relay P1 prevents the called subscriber from receiving further calls by short-circuiting the high resistance winding P1.II at P1.37, and holds on through winding P1.1 and contact P1.37. Preparation for and transmission of messages. The circuits are prepared for message-sending by depression of the key ST. Relay X at the calling station operates, holds on via X.1, connects lead a to the sender JS at X.3, and cuts out the lineselector relay A<1> at X.2. Relay X1 is thereupon energized via A1.32 and P1.39, and puts the leads a, b through by moving its contacts X,.42, 43 to the right, the slow release relay C1 being thus held on via contact TR.51. Repeater coil E, passes on the reverse-polarity impulses by attracting the armature E1.56, thus calling the called station through its receiving relay as at E. The message is signalled by reversal of current by the sending instrument JS. Clearing signal. This is effected by interruption of the circuit a, b on depression of the switch TT. Relays X, TR thereupon release, cutting out relays C1 and P. Relay C is consequently short-circuited at P.20, cutting out, at C1.34, line-selector relay P, and called-preseleotor relay T. On release of P, the switching magnet D2 is cut in at P,.38. Windings D2, U.II, and contacts D2.58, U.50 then co-operate to produce intermittent actuation and thus zeroize the lineswitch. Contacts K1.53, 54 are thereupon broken and interrupt the cycle. All line selectors engaged. If the line-selector wiper c fails to find a disengaged contact, the wipers are moved to their end position, where the contact W.2 cuts in relay J.II and halts the switch, while contact W.1 cuts in the busy signal. which is transmitted through transformer U2 and windings A acting as a transformer. The switchhook is replaced, cutting out the relay A which short-circuits relay C at A.15. Winding J.II is cut off at C.9 and cuts in the switching magnet D, at J.18; this magnet then zeroizes itself. ultimately restoring contacts K.25, 26, which cuts it out.