Patent GB-779414-A (GB)
Title: Improvements in or relating to telephone systems
Inventor: HOPLEY HORACE EDWARD
IPC: H04Q3/00
Filed: 1954-10-26
Abstract: 779,414. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd. Sept. 12, 1955 [Oct. 26, 1954], No. 30770/54. Class 40 (4). In a cross-bar exchange the transmission relay sets have access to subscribers' lines over a line finder/final selector stage in which the cross-bar switches are arranged for link working and in which each cross-bar switch consists of a primary switching portion and a secondary switching portion, the links from the bridges of a primary switching portion of one switch extending to bridges of the secondary switching portion of another switch. The transmission relay sets have access to both-way junction sets over a further cross-bar switch which also serves to connect any transmission relay set with any one of a number of register/discriminators. The invention is described as applied to a satellite exchange serving eighty ordinary subscribers and ten party lines each having a maximum of seven subscribers, and providing both-way working over seven junctions to a main exchange. The satellite uses six crossbar switches of the 12 X 10 type, each arranged for double-group working. Each of the switches 1SA to 4SA, which together constitute the line finder/final selector stage for the eighty regular subscribers' line circuits SLC11 to 80, is divided; bridges BR1 to BR5 constituting a primary switch, and bridges BR6 to BR10 a secondary switch. Twenty subscribers' lines are multipled to the bridges of each primary switch PRI1 to PRI4, and the secondary switches SEC1 to SEC4 are internally multipled; the twenty outlets providing originating trunks ORIG1 to ORIG10 and terminating trunks TERM1 to TERM10 which are multipled to all the secondary switches and to switch SB which serves the party line circuits PLC91 to PLC90. Primary/ secondary working is not used for the lastnamed circuits which extend directly to the bridges of switch SB. Each of the transmission relay sets TRS1 to TRS10 incorporates a speaking bridge, call supervision equipment and ringing current and audible tone sources, a single repeat metering equipment RME being provided in common to the ten relay sets. The common marker MKR is associated with a cyclic allotter ALL which in the case of locally originated calls selects a transmission relay set, a both-way junction set BJRS1 to BJRS7 and a register/discriminator RD1 to RD3 the latter having access to a common tariff indicator TI. The register/discriminators are terminated directly on the bridge commons of bridges BR1 to BR3 of switch SC and each may be connected to any of TRS1 to TRS10. The remaining bridges BR4 to BR10 are separately associated with BJRS1 to BJRS7 respectively and enable any of these junction relay sets used in either an incoming or an outgoing capacity to be connected to the originating or terminating side respectively of any transmission relay set. The transmission relay sets, the register/discriminators, and the both-way junction relay sets are arranged in closed chains for testing purposes and in each case three test start leads are provided which are energized successively by successive seizures of the allotter, so that testing begins at a different point in each chain on each occasion. Regular subscriber initiates a call. If line circuit SLC20 calls the marker receives from it a marking indicative of " 20 " and controls the operation of magnets SM10 and AM2 in switch 1SA and magnet AM1 of 2SA. The allotter, taken into use by the marker, applies a signal to a start lead T1, T2 or T3 and the first idle transmission relay set, say TRS10, is seized, causing the operation of magnets SM10 and AM1 of switch SC. An idle register/discriminator (RD2) and junction relay set (BJRS5) are seized and cause the operation of magnets BR2 and BR8 of switch SC, thus connecting up RD2 and BJRS5 to TRS10. The seizure of TRS10 also causes the operation of SM10 in switch 2SA and the marker tests the relevant links L1 to L5, operating the bridge magnets corresponding to the first idle link in the primary and secondary switches, after which the marker and allotter are released. Dial tone is reverted from the parent exchange and the dialled digits are repeated by TRS10 to RD2 and also over the junction J5 to the parent exchange. For local calls five digits are required, discrimination being effected on the second digit (junction relay set released and bridge magnet of SC relevant thereto restored) ; and the third digit determining whether the call is to a party line (" 9 ") or regular subscriber. Call to regular subscriber "71". The fourth and fifth digits ("71") are recorded by the register discriminator which seizes the marker and transfers them thereto. The marker thereupon operates magnets SM1 and AM1 of switch 4SA, a signal from the allotter (initiated by the register/discriminator) operates magnets AM2 in switch 1SA, and the marker, in conjunction with TRS10 and the allotter, operates SM10 in the same switch. The marker tests for and takes into use a free link between PRI4 and SEC1, the relevant bridge magnets in 1SA and 4SA being operated to complete a connection from TRS10 to the called line. The register/ discriminator, allotter and marker, together with the relevant connection over switch SC, are released. Call to party line subscriber. The connection from the relay set TRS10 to the party line circuit is set up over switch SB, in accordance with the third and fourth digits (in the range "91" to "90 ") defining the wanted party line, by the marker and allotter, and the fifth digit ("1" to " 7 ") defining the particular subscriber is sent by the register/discriminator as a pulse series over switch SC to TRS10 which repeats it to condition the party line circuit for the ringing of the wanted party. Call to subscriber outside the local multiexchange network. The first two digits, say " 0 " and another, are effective in the register/ discriminator to indicate such a call, and the digits continue to be transmitted over the junction. The second and third digits are also stored in the register/discriminator which transfers them to the tariff indicator T1 which returns a signal, indicative of the meter free to be charged, via switch SC to TRS10 which is set to direct an appropriate series of metering pulses from RME to the caller's meter at the end of each timed period of the call. The register/discriminator and tariff indicator are then released. Incoming call. The seized both-way junction relay set takes the marker into use, and the allotter causes the seizure of an idle transmission relay set and an idle register/discriminator and the establishment of connections over switch SC from the junction relay set and from the register/discriminator to the transmission relay set. The allotter and marker are released and the incoming junction loop is extended to the transmission relay set which receives the remaining dialled digits and repeats them to the register/discriminator. The connection to the wanted party is then completed as for a locally originated call.