Patent GB-120197-A (GB)
Title: Improvements in or relating to Automatic Telephone Systems.
IPC: H04Q3/62
Filed: 1918-08-08
Abstract: 120,197. Automatic Telephone Manufacturing Co., (Assignees of Richardson, R. G.). Oct. 13, 1917, [Convention date]. Automatic and semi-automatic exchange systems.-A call from a main exchange to a private branch exchange can be transferred from one subscriber to another in the branch exchange, without first releasing the connexion to the main exchange. The transfer is initiated by the called party momentarily depressing his switch hook to release the connector through which he has been called, and the connector is then again operated to select a third party either by the calling or called party. The connexion with the party first called may be released automatically upon the response of the second called party, or, alternatively, when the first called party replaces his receiver, this arrangement providing for the three parties being in conversation. The first called party may be an operator who answers all calls to the branch exchange, and then extends them to the wanted party. In the arrangement described, a trunk 2, 3, Fig. 1, incoming from the main exchange terminates in a connector D which is operated to extend the call to the subscribers of the branch exchange, two of whom are shown at A, A<1>, Fig. 2. The branch exchange lines A. A<1> terminate in rotary line switches C, C<1>, by which they are connected to the trunks, such as 130, 131, 132, terminating in local connectors for local and outgoing main-exchange calls. The rotary switches C, C<1> also have access to trunks, such as 85 - - 88, individual to the connectors, such as D, Fig. 1, handling incoming calls. When a call incoming over the trunk 2, 3 has been extended by the connector D over its wipers 61 - - 64 to a party A, and the latter, wishing to transfer the call to a party A<1>, depresses his switch-hook, his rotary switch C operates to extend his line over the wipers 110 - - 113 to the leads 85 - - 88 individual to the connector D, whereupon the latter is released and can then be operated again either by the party A or by the calling party over the trunk 2, 3. The operation in further detail is as follows :- Operation of connector D, Fig. 1, to select party A, Fig. 2. When the trunk 2, 3 is taken into use at the main exchange, the relays 4, 5 are energized in the usual manner, and the last two sets of selecting-impulses are repeated to the vertical magnet 18 and the rotary magnet 19, the sideswitch being moved into its second and third positions by the private magnet 17 under control of the slow-release relay 16. Busy test and busy signal. If the wanted line A is busy, its test terminal 72 is earthed either directly or through an auxiliary battery B, and a circuit is therefore closed through the test wiper 62, side-switch arm 24, winding of test relay 11, and the private magnet 17, which locks the sideswitch in the second position. Relay 11 locks up over its armature 44, and connects a busy generator Q to the calling line. Operation if called line is free. In this event, the side-switch moves into its third position, completing a circuit through the stepping-magnet 104 of switch C, cut-off relay 102, wire 82, terminal 72, wiper 62, switch arm 24, and auxiliary battery B to ground. Magnet 104 is prevented from energizing by the resistance of relay 102, which, owing to an interlocking-arrangement between the armatures of relays 102, 103 is not able to fully attract its armature, so that the wipers of the line switch C remain disconnected, Ringing-current. A relay 15, energized in parallel with relay 102, closes the ringing-circuit from the generator Gen over armatures 41, 55, line of station A, armatures 54, 37, and the upper winding of the ring-cut-off relay 10. When the called party replies, relay 10 is energized, locks up over its lower winding, disconnects the ringing-generator, and completes the through talking-circuit, the back-bridge relay 9 being at once energized over the called line. Transfer of call to third party. If the call is to be transferred, the called party A releases the connector D by momentarily depressing his switch hook, whereby the following sequence of operations occurs. The opening of the line circuit of the called party de-energizes relay 9, thereby closing a circuit over armatures 36, 39 through the test relay 11 and private magnet 17. Relay 11 locks up over its armature 44 and prepares a circuit for the upper winding of relay 12 which is completed a moment later over armature 35 when the called line circuit is again closed. Relay 12 locks up over its lower armature and by attracting its upper armature removes the ground connexion from lead 87 and terminal 120 and its multiples in the switches C, C', &c. Relay 12 also closes circuits (1) through a relay 13 and a common relay 25, which prevents the energization of the relays 12 of other incoming connectors during the operation of the switch C, and (2) through the stepping- magnet 104 of switch C, wire 80, wiper 60, relay 14, armatures 51, 48, wiper 63, wire 83, and wiper 112 of switch C to earth. Relay 14 is energized to maintain this latter circuit before relay 13 attracts its armature 51. The stepping-magnet 104 interrupts its own circuit and thus steps round the wipers 110 - - 113 as long as the wiper 112 engages grounded terminals. The terminals 116 of the local connector trunks, such as 130, 131, 132, are permanently earthed, so that the switch C rotates until its wiper 112 reaches the terminal 120 of trunk 85 - - 88 from which ground has been removed by the energization of relay 12. During this movement, the cut-off relay 102 has been energized by current from the auxiliary battery B, and the relay 14 has been energized in series with the stepping-magnet 104. When the wipers of. the switch C reach the terminals 118 - - 121 of the connector D, the circuit of the magnet 104 and relay 14 is opened, and the latter energizes the connector release magnet 20 over armatures 50, 52. The connector is then restored to its normal position, opening the circuit of the cut-off relay 102, which de-energizes and closes a circuit for the line relay 103, which at once closes a further circuit for the cut-off relay 102, which now extends the line of party A over its wipers 110, 111, and leads 85, 86 to the windings of relay 8 of the connector D. As soon as the connector is completely restored, the locking-circuits of relays 10, 11, 12 are opened, and relay 12 opens the circuit of relays 13, 25. The connector can then be set on the terminals of a third party by the calling party through relays 4, 5 as before, or by the first called party through relay 8, which energizes a slow-release relay 7, and then repeats the selecting-impulses over armatures 36, 34, 31 to the relay 16 and vertical and rotary magnets 18, 19. The connector acts as previously described to test and ring the wanted party. During the setting of the connector, the relay 6 is energized to disconnect the calling line. When the called party replies, the relays 10, 9 are energized as before, and the connexion to the calling party is completed. The three parties are now in talking connexion, and the first called party may then hang up, thereby releasing his connexion with the connector D. In a modification, in which the armature 33 of relay 8, instead of being directly earthed, is connected to the relay 34 as indicated by the dotted line, the connexion with the first called party is released directly the second called party answers.