Patent GB-250304-A (GB)
Title: Improvements in or relating to telephone exchange systems
IPC: H04M3/523
Filed: 1925-01-01
Abstract: 250,304. Western Electric Co., Ltd., (Arntzenius, C. R. H.). Jan. 1, 1925. Automatic, semi-automatic, and manual exchange systems.-In a switching arrangement for connecting lines of an incoming group of lines, which may be taken into use in any order, to idle trunks of a smaller group of outgoing trunks, means are provided whereby when all the outgoing trunks are busy, incoming lines which await connection are connected to outgoing trunks as they become free, in the order in which the incoming lines were taken into use. Two operators' positions are shown in Figs. 1 and 2, from which access may be had to five reserve lines R1 - - R5, Fig. 3, adapted to be extended, as they are taken into use, over the connecting relays shown in Fig. 4 to idle two-way toll trunks a - - d. Groups of relays associated with each reserve line are connected in chain circuits with one another and with corresponding relays of other reserve lines, in such a manner that the reserve lines are connected to idle trunk lines in the order in which they are taken into use, their order in file being indicated to the operators by preference lamps. The invention is described in its application to a method of making trunk calls between distant manual exchanges through an intermediate manual exchange, the connection through the intermediate manual exchange being effected either manually by operators or automatically bv switches controlled by the operator at the exchange of origin. Arrangement for connecting operators to toll trunks, Figs. 1 to 4; reserve line circuits. -Assuming that on pressing the busy key 146 all the reserve lines R1 - - R5, Fig. 3, are shown by the busy iamps 21, 22, &c. to be free, on plugging into a multiple jack 1 of the first line R1, the busy relay b<1>1, Fig. 3, is energized over a relay 140 and prepares a circuit for a busy lamps 21, 22. The first cascade relay 50 energizes over the chain of left-hand contacts of subsequent relays 51 - - 54 and the chain of left-hand contacts of first cascade relavs 55, 60, 65, 70 of other reserve lines, and closes a circuit for the second cascade relay 51 over the chain of inner right-hand contacts of the second cascade relays 56, 61, 66, 71. The second cascade relay 51 opens the circuit of the first cascade relay 50 and closes a chain circuit for the third relay 52, which de-energizes the second relay 51 and energizes the fourth relay 53, which in turn de-energizes the third relay 52 and energizes the fifth relay 54. The fifth relay 54 remains held until the plug 135 is pulled down, opens the circuit of the fourth relay 53, and by connecting battery to the third wire R1 causes the reserve line to be connected to an idle one of the toll lines a - - d, as described later. Assuming now that the second reserve line is taken into use, the cascade relays 55 - - 58 energize in succession, but the energization stops at the fourth relay 58 since the chain circuit nf the fifth relay 59 is opened by the fifth relay 54 of the first reserve line. Similarly, when the third and fourth reserve lines are taken into use energization of the cascade relays stops at the third and second relays respectively. The operation is similar no matter in what order the reserve lines are taken into use. Should a fifth reserve line be taken into use when all the four junction lines are engaged, only the first cascade relay such as 70 is energized, and since it has no provision for connecting battery to the third wire E1, its energization is of no effect other than lighting preference lamps 15, 20 at the multiple jack positions. When one of the, toll lines is freed by the removal of a reserve line jack, the adjacent cascade relay, say the fourth, relapses. The fourth cascade relay in another reserve line in which the third relay is at this time energized now pulls up and opens the circuit of the third cascade relay, which in turn closes the circuit of the third relay in another reserve line in which the second relay is energized. The relapse of this second relay permits the second cascade relay such as 71 in the waiting fifth reserve line to energize, connect battery to the third wire E1 to initiate the seizure of the idle junction line, and de-energize the first relay 70 which extinguishes the preference lamps 15, 20. If the toll group comprises only three lines, keys S1 - - S5 and S6 - - S10 in the vertical rows of the first and second cascade relays are pushed down, and two reserve lines are able to wait in a prepared condition. Plugging into a jack of a last but one reserve line energizes the second cascade relay giving this reserve line first preference and fully lighting the preference lamps. Plugging into a jack of the last reserve line energizes the first cascade relay and gives the line second preference, only half-lighting the preference lamps, since a resistance such as W1 is included in series. When a toll line is freed, the reserve line with the fully lighted lamps gets the connection, but the second preference line wih the half lighted lamps then becomes first preference and its lamps are fully lighted. An operator waiting on a reserve line may know when her line has become connected to a toll line by throwing a key (not shown) to prepare the circuit of a lamp 130 and noting when this lamp lights up. The relay 140 is energized over parallel branch circuits, including respectively the relay b<1> and the locking winding of the energized first cascade relav. The latter branch includes a resistance W5 which does not permit the relay 140 to respond. When, however, a toll line falls idle and the waiting reserve line is connected up, a second cascade relay is locked up in place of the first. The locking circuit of this relay does not include a resistance and the relay 140 responds and lights the lamp 130. If three toll lines only are working, the key S11 is thrown to insert a similar resistance W7 in the locking circuits of the second cascade relays. An operator having an urgent call can ring another operator waiting on a reserve line and take into use this reserve line for her call. The original operator will then throw her key to connect up the lamp such as 130, but as two relays such as 140 will not respond in parallel the lamp will not light until the other operator has finished her call. Connection with idle toll line. Each reserve line is provided with a connecting relay 75 - - 78 for each toll line. These connecting relays are so arranged that only one in a vertical row can be energized at any moment. Assuming that all the junction lines are idle when a reserve line, say the line R1, is taken into use, when the third wire A1 is connected to battery over an armature of a. cascade relay, a circuit is completed for the connecting relay 75 of the first toll line a, a switch-through relay 95, and a cutoff relay 99. over chain contacts of the horizontal relay row 75 - - 78, a back contact of the relay 95, and chain contacts of the vertical relay row 75, 79, 83, 87, 91. Relay 75 holds over its righthand winding, connects the reserve line R1 to the first toll line a, and opens the circuits of the other horizontal relays 76 - - 78. Relay 95 switches through the connecting circuits to the vertical row of relays 76, 80, 84, 88, 92 associated with the second toll line b, so that if another reserve line is taken into use, one of these relays and the relay 96 are energized. Assuming a reserve line is plugged when all the toll lines are busy, the reserve line is prepared as described in the previous paragraph. When one of the toll lines, say the toll line b, falls free, the corresponding connecting relay 76, 80, 84, 88, or 92 and the switch through relay 96 are de-energized, but a moment later the connection of battery to the third wire of the waiting reserve line causes it to be extended to the freed line. If a toll line is out of service, a key 107 - - 110 is operated and the appropriate switch-through relay 95 - - 98 energized : the connecting circuits from the reserve lines are thereby caused to skip the vertical relay row of the out-of-service line. To reduce the number of series contacts in the toll lines, the contacts of the connecting relays may make, parallel connections with the toll lines. Incoming calls. An incoming call over a free toll line, say c, energizes a calling relay 105, which holds over its left-hand winding, lights calling multiple lamps 122, 123, Figs. 1 and 2, and energizes the switch-through relays 95, 96 98 of all other idle toll lines, in order that when an operator plugs into a free reserve line connection is immediately made with the calling toll line. If two incoming cal's, say over junctions a and c. arrive simultaneously, the first reserve line which is plugged is connected to the first junction a. The cut-off relay 99 opens the holding circuit of the calling relay 103, but the multiple lamps 122. 123 are held energized by the calling relay 105 until a second reserve line is plugged and connected to the junction c, when the cut-off relay 101 de-energizes the calling relay 105 and extinguishes the calling lamps. Calls through an intermediate exchange, Fig. 7, indicates diagrammatically an intermediate exchange equipped with two operators' positions Y21, Y21, each having four groups of reserve line jacks, lamps, &c. for obtaining access through cascade and connecting relay groups U1 - - U4 to four groups of junction lines u1, u2, z1 - - z3, u3, and m1 - - m4 leading to four other exchanges, two of which are indicated in Figs. 5 and 8. Assuming that a connection is required from the exchange shown in Fig. 5 to that shown in Fig. 8, an operator at the first exchange plugs into a free reserve line jack, and as previously described obtains connection with an idle junction z<1> terminating in the intermediate exchange, Fig. 7. Ringing current is then projected over the junction and energizes a calling relay o23