Patent GB-233882-A (GB)
Title: Improvements in or relating to automatic and semi-automatic telephone exchange systems
IPC: H04M3/58
Filed: 1924-05-12
Abstract: 233,882. Coventry Automatic Telephones, Ltd., (McBerty, F. R.). May 12, 1924. Automatic and semi-automatic exchange systems.-A called subscriber, desiring to speak temporarily with a third party, may, by dialling the third party's number, disconnect himself from the original calling party without however releasing the connection and connect himself over an auxiliary circuit to the third party. When the third party hangs up, the auxiliary circuit is disconnected and the original connection restored. If the third party is busy or does not reply, the release of the auxiliary circuit and the restoration of the original connection are effected by the called party dialling the digit O. The invention is described with reference to a small private branch exchange of 25 lines, similar to that shown in Specification 219,456, in which connections are completed over connecting circuits by group and units connecting-relays arranged non-decimally and controlled by a single relay counting-chain. A call from a subscriber A, Fig. 1, at a manual main exchange to a wanted P.B.X. subscriber B, Fig. 2, is completed by the P.B.X. operator D. If subscriber B now operates his dial to call a third party C, Fig. 3, relay 46 disconnects the called end of the connecting circuit, Figs. 1, 2, from the calling end A and connects it over conductors 79 to an auxiliary link, Fig. 3, the temporary connection being completed over group and units relays 190, 180 selected by the same relay chain 60 - - 70, Fig. 2, which was employed for establishing the original connection. Relay 46 is de-energized and the original connection restored by subscriber C hanging up or by subscriber B dialling the digit O. The connection to a third party may be repeated any number of times, and may even be to a subscriber at a distant exchange since the connecting relays 80, 90, 180, 190 have contacts associated with trunks leading to other exchanges. Call to subscriber B (No. 31); selection of wanted line. The P.B.X. operator D answers an incoming call by throwing her key 4 upwards and, on ascertaining the wanted number, throws it in the opposite direction to bridge her set across the trunk, thereby operating line relay 10. She also operates key 6 to hold the incoming end of the connection and to light trunk-busy lamp 8. Relay 10 closes a circuit for relay 12 of the first idle connection-circuit to which the connection is then extended by group and units relays 30, 20. Relay 40 operates and completes a circuit for slowrelease relay 11 in series with a change-over relay 41 made slow to energize by a shunt resistance. Relay 40 also energizes relay 60 of the counting chain, whilst relay 11 locks up relays 20, 30 and operates the cut-off relay 9. The first digit of three impulses is repeated at the left-hand armature of relay 40 and results in the looking up of counting relays 65, 66. At the end of the digit, relay 41, which remained de-energized during impulsing, re-energizes and completes a circuit over the lowest contacts of relay 65 and the uppermost contacts of relay 66 for the group relay 90 which locks up over contacts of relays 11, 13. Relay 90 completes a circuit for relay 45, which unlocks relays 65, 66 to restore the counting chain to normal. Relay 45 also completes a circuit for relay 44 which locks up, opens the circuit of relay 45, and closes the starting circuit 73 for the busytone machine 75. Upon the relapse of relay 45, relay 47 energizes and relay 60 operates again. The single impulse of the second digit locks up relays 61, 62 and the subsequent operation of relay 41 completes a circuit for units relay 80. Busy test and release. If the wanted subscriber is busy, the cut-off relay 9<b> is energized over a direct ground or over a relay similar to relay 72. In either case relay 72 does not operate and busy tone is transmitted over the upper talking conductor to the operator D who informs the calling subscriber. When the operator hangs up, re- Jays 40, 11, 9 de-energize and relays 20, 30, 80, 90 are unlocked. Ringing; called subscriber's reply. If the called line is idle, relay 72 operates in series with relay 9b, energizes relay 45 to restore the counting chain, and grounds lead 74 to start up the ring- ing interrupter 78 which it also connects up so that relay 77 is intermittently energized to supply ringing current 76. When the called subscriber replies, relay 50 operates, disconnects relays 44, 45, energizes slow-release relay 42 and slow-to-energize relay 43, so that a new circuit for relay 60 is now completed over front contacts of relays 40, 42, 50, 72. Relay 42 completes circuits for relays 13, 14, the former placing the locking circuits of relays 20, 30, 80, 90 under the control of the called party, the latter placing holding bridges across the trunk on either side of the condensers 5. The lighting of lamp 16 indicates the called subscriber's reply, and the opeartor restores keys 4, 6 and hangs up. Calling a third party C (No. 11). When subscriber B operates his dial for the first digit, the single impulse is repeated at the right-hand back contact of relay 50 and results in the operation of relays 61, 62 as before. Relay 62 completes a circuit over its uppermost contact for relay 46 which disconnects the called end of the connecting circuit from the calling end and connects it to conductors 79, the marking wires from the relay counting-chain being similarly transferred. Relay 46 also completes a circuit for relay 102 which in turn energizes a relav 104 in the first idle auxiliary connecting-circuit. Relays 102, 104 energize relay 100 to connect conductors 79 to the auxiliary connecting circuit, and relays 101, 105 also operate. During the impulsing, relay 43 remains de-energized and short-circuits relav 41 which is thus also de-energized. At the end of the digit, the operation of relay 41 completes a circuit over contacts of relays 107, 100, 46, 61, 41, 62, 47, 46, 100 for connecting relay 190 which locks up and energizes relay 107 to unlock relays 61, 62 and restore the counting chain to normal. Relay 107 also energizes relay 106 which locks up and releases relay 107 whereupon relay 47 is energized, so that the second digit in a similar manner results in the closure of a circuit for relay 180. Ringing now takes place in a manner similar to that for subscriber B, and when subscriber C removes his receiver, relay 150 energizes and the temporary conversation proceeds. Release of third-party connection. When subscriber C hangs up, the release of relay 150 causes a momentary circuit to be completed for relay 71 which unlocks relay 46 and restores the connection between subscribers A, B. Relays 101, 105, 100, 180, 190, are all released and the auxiliary circuit is thus restored to normal. If subscriber C is busy or does not reply, the transmission of the digit O by subscriber B causes the successive energization of relays 61 - - 70, the sixth impulse operating relay 71 to release relay 46 as before. Release of original connection. When subscriber B hangs up, relays 50, 42, 43 release, relay 42 unlocking the circuits of relays 20, 30, 80, 90, so that relays 13, 11, 14, 7 are de-energized and lamp 8 extinguished All auxiliary connecting-circuits busy. In this case, the operation of one of the relays 102, 102<1>, &c. completes a circuit for the starting conductor 173 of the busy-tone machine, and busy-tone is supplied to the upper talking conductor. Specifications 196,018 and 197,630 also are referred to. 233,957. Siemens Bros. & Co., Ltd., and Patterson, W. G. Sept. 16, 1924. Addition to 203,759. Automatic exchange systems.-The connector of the parent Specification has an extra bank in which ordinary lines are distinguished from lines to Private Branch Exchanges independently of the ordinary test circuit, and an extra wiper connected to a relay which causes the connector to hunt when set to the first line of a group. According to the present invention, the distinction between the first line of a group and an ordinary line exists only while there is an idle line in the group. If desired the distinguishing mark may be removed from all the lines when a group becomes busy so that. if a connector is hunting it is stopped at once and gives a busy signal. In the extra bank of the connector described, ordinary lines and last lines of groups are dead, intermediate lines are permanently grounded, and each first line is connected to a wire such as u which is connected to ground over normal contacts of all the line switches D1, Fig. 2, of the group and contacts of their cut-off relays BB. Alternatively ordinary lines and last lines may be grounded and other P.B.X. lines left dead. The extra wiper X<0> is provided with a trailing arm which short-circuits the hunting-controlling relay PR when (for example at night) the connector is set to an intermediate line by dialling. Control of connector by dialled impulses. Line rely A energizes release relay B and the tens digit is repeated to vertical magnet VM and series relay C. Vertical springs k1, k2 change over and the relapse of relay C energizes winding 1 of relay G which connects up the rotary magnet RM for the units train. After the change-over of rotary spring w1, relay G is held over its winding 2 and a front contact of series :relay C. The relapse of relay C connects winding 2 of relay G over both windings of relay H to the test wiper C‹. Busy test and signal. If the line is busy wiper C‹ is substantially at ground potential and relay G falls sluggishly and, if the hunting-controlling relay PR is un-energized, energizes relay F to connect the busy wire BB to the lower talking wire. Hunting for an idle line to a P.B.X. If the connector is set to the busy first line of a groupcontaining an idle line, relay PR pulls up over its winding 1 and wiper X<0> when relay C falls back, and the subsequent relapse of relay G energizes rotary magnet RM a