Patent GB-262177-A (GB)
Title: Improvements in telephone systems
IPC: H04M5/08
Filed: 1925-09-01
Abstract: 262,177. Western Electric Co., Ltd., (Bell Telephone Laboratories, Inc.). Sept. 1, 1925. Manual exchange systems.-In a system in which, upon the seizure of any idle inter-exchange trunk C by a calling A-operator, Fig. 1, a finder-switch 60, Fig. 2, connects the seized trunk to the telephone set OT of a distant B-operator who completes the connection with any idle cord on her position, the act of inserting the plug 65 into the jack of the wanted line 100 causing a second finder-switch 80 to connect the seized plug to the calling trunk, provision is made whereby, if the B-operator takes down the plug before the A-operator releases the trunk, the former is given an intermittent signal. Provision is also made whereby the called line 100 is rung automatically, and this automatic ringing is repeated and the connection to the trunk C is maintained if the plug 65 is transferred from one jack to another. An A-operator seizing a trunk leading to an unattended B-position is given a distinctive signal. Connection of B-operator's set OT to calling trunk C. When the A- operator plugs into the jack 16, relay 40 completes a circuit for relays 41, 42, the latter lighting a lamp 43 and completing a stepping-circuit for magnet 44 of the finder 60 which rotates until wiper 50 reaches the terminal associated with the trunk C. Relay 42 is then shunted by relay 45 and releases, whilst relay 45 energizes to light lamp 46 and to complete a circuit for relay 47 which momentarily operates and connects up a tone signal AT to inform the A-operator that she may communicate the wanted number. Relay 47 also connects up relay 48 which locks up in series with relay 49, thus causing the release of relay 47 and the connection of the operator's set OT to the trunk C. Wanted line busy. The B-operator tests the wanted line in the usual way with the tip of the calling plug, and.if the line is busy, she depresses one of the keys 61, 62, thus causing the operation of relay 91 over wiper 51 and the connection of an interrupter 93 and busy tone transformer BBT to the trunk C. The interrupter causes the intermittent operation of relay 84. which by intermittently shunting the left-hand winding of relay 40 causes the relay 18 to flash the A-operator's supervisory lamp 19. Relay 91 releases relays 41, 45, 49, 48 disconnecting the operator's set OT from the trunk. Connection of seized plug to trunk C. If the line is idle, plug 65 is fully inserted, causing the operation of relay 67 which lights lamp 68, and completes a stepping circuit for magnet 69 of switch 80. When the trunk C is reached, wiper 83 completes a circuit for relays 71, 70, the former releasing relays 41, 45 and locking up to battery supplied by relay 40, whilst relay 70 extinguishes lamp 68 and operates relay 73 which completes two locking circuits, dependent respectively upon relays 40, 67. Ringing. Relay 70 also completes a circuitfor relay 71 which applies ringing-current from generator 76 to the wanted line. When the subscriber replies, relay 74 energizes and removes a short-circuit from relay 75 which operates to cut off the ringing and to complete the connection. Relay 84 energizes over the called line and shunts relay 40 to cause the extinguishment of lamp 19. Release; attracting operator's attention. When the A-operator removes the plug 15, relays 40, 71, 70, 72, 75 release and lamp 68 is lit. The removal of plug 65 releases relays 67, 73. If thecalled subscriber has not hung up when plug 15 is removed, relay 94 completes a flash circuit for lamp 68, and if he desires to re-establish the connection he may attract the B-operator's attention by moving his switch hook up and down, thus causing the lamp to glow end flash alternately. If plug 65 is accidentally removed' before the conversation is concluded, the lamp 68 is flashed over interrupter 76. Transferring plug from one wanted party to another. If, with the trunk C held, the B- operator inserts the plug 65 first into the jack, say, of an information operator and then transfers it to a wanted subscriber, both called parties will be rung as above and the plug will remain connected to the trunk owing to the locking circuit of relays 70, 73, which is dependent only on relay 40. Unoccupied position. A key 90 is thrown at an unoccupied B-operator's position, and if an A-operator seizes a trunk to such a position, relay 91 is energized over wiper 51 after switch 60 has seized the trunk, and a special tone OBT is transmitted to the A-operator.