Patent GB-269152-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/42
Filed: 1927-03-21
Abstract: 269,152. Associated Telephone & Telegraph Co., (Assignees of Richardson, R. G.). April 8, 1926, [Convention date]. Automatic exchange systems.-In order to be able to use consecutive numbers for private branch exchange lines and to increase the number of trunks leading to a P.B.X. without making previous provision and without altering its number, the last two digits of the P.B.X. number operate a register sender associated with the trunk chosen by the previous selectors; the sender comprises an intermediate distributing frame which translates the stored digits into three routing digits which operate a special selector S, reached over a line switch RLS, and a rotary connector RC which thereupon hunts for an idle line to the PBX. The last two dialled digits operate a register switch R, the three wipers of which pick out contacts crossconnected to contacts in the sender switch SS in accordance with the nosition of the required P.B.X lines in the banks of the connectors. As shewn, the P.B.X. has five lines multipled to the last five contacts of the fifth level of the connectors RC multipled in the third level of the selectors S. so that the translated number is 356: to obtain ten lines for this P.B.X. it might be necessary to transfer it to the eighth level of the second group of connectors, in which case the terminals 131 - - 133 would be jumpered to the contacts 281 of the switch SS, but the dialling number for the P.B.X. would remain unchanged. The trunk 2, 3, 4, is only selectable if, besides being itself idle, it is connected through an associated selector RSS to an idle register sender. The selectors RSS of a group of trunks are controlled by a marginal relay 5, Fig. 1, which is operated when only two trunks are connected to idle register-senders to set the selectors hunting, and is de-energized when two more trunks have found idle senders. Seizure of register-sender. The first two digits dialled operated the first and second selectors to choose an idle trunk which is associated with an idle register sender. Earth is immediately put on conductor 3 to busy the trunk and also the associated sender over armature 25 and wiper 39 of the register sender selector RSS. Relay 140, Fig. 2, operates. Line and release relays 11, 12 operate as usual, and also relay 13, which is slow to operate to prevent magnet 35 energizing. Relay 30 now energizes to connect up the register sender. The line switch RLS is now operated over the loop (line 52, wiper 37, line 41', armature 149, and spring 164, line 42<1>, wiper 38, line 54) and selects an idle special selector S. Registering digits. The interruptions of the circuit of the relay 11 due to the next digit send impulses to relay 105 and vertical magnet 117 of the register R in series over wiper 40 and the off-normal springs 114, 115 in turn. The first impulse of the last digit dialled operates relay 106 and rotary magnet 118 in series and relay 107 is then energized and locked up to earth at armature 144. At the end of the digit, the wipers 121 - - 123 engage the required contacts. Impulse sending. At the termination of the impulses, relay 106 de-energizes and an impulsing sending circuit is closed (earth, interrupter I, armatures 120, 113, 147, magnet 160 to battery). When magnet 160 de-energizes, wipers 161, 162 are advanced to contacts 171, 171<1> and relay 142 is energized to feed back earth at armature 150. to energize magnet 101 of the sequence switch SS<1>, and to remove the shortcircuit at armature 149 from 'the impulsing springs 164. At the next energization of magnet 160, an impulse is sent from the springs 164 and then the wipers are stepped on to contacts 172, 172'. Two more impulses are sent before contacts 174. 174<1> are reached, when shunt relay 141 is energized over wipers 162. 103 and locks up over armature 148. The springs 164 are shorted, the impulsing circuit for the magnet 160 is opened, and a self-interrupting circuit therefor is closed over armature 147, springs 163 and wiper 161 to step the switch SS to normal, when relays 142, 141 release in turn and give time for the selector S to hunt for an idle connector RC. Magnet 101 is also de-energized to step the switch SS<1> to its second contacts. Impulses are again sent as before, five impulses being sent to the vertical magnet of the connector, and the switch SS<1> is stepped to its third contacts. The last set of impulses operates to rotate the wipers 72 - - 74 to the first trunk of the desired P.B.X., and the connector then hunts for an idle trunk in known manner. The switch SS<1> is now on its fourth contacts. Completion of connection and release of register sender. Switching relay 14, Fig. 1, now operates over wipers 40, 103 and locks up to line 3 switching the talking circuit through and deenergizing relays 11, 12, 30, and 140. The release magnet 119 now operates to restore the sender to normal, while the magnet 101 is energized in a self-interrupting circuit over wiper 102 to step the switch SS<1> to normal position 102<2>, 103<2>. The connector RC signals the P.B.X. operator, who completes the connection to the desired subscriber. Release. When the called subscriber hangs up. the P.B.X. operator takes down the connection, while release of the train of switches is initiated in well-known manner when the calling subscriber hangs up. Operation of register-sender selectors. Each trunk 2, 3, 4 is busied, when it is in use itself or when the associated register-sender is busy, earth being fed back to the conductor 3 either from the connector RC, or over wiper 39. In either case, relay 13 operates to prepare a circuit for magnet 35 of selector RSS, and to short circuit the resistance 27 which is in series with a marginal relav 5 and other resistances such as 27' in the other trunk circuits of a group. Relay 5 operates when all the resistances 27, 27<1> except two are shorted, and the magnets 35 of the switches RSS connected to busy senders are selfstepped to find idle senders. Relay 5 remains operated until four resistances are in its circuit, when the circuits for magnets 35 which are still hunting are broken.