Patent GB-180670-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1922-05-19
Abstract: 180,670. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Gardner, J. E.). May 25, 1921. Automatic and semi-automatic exchange sys. tems.-A selector in an automatic private branch exchange has its first nine levels of bank contacts wired to connectors for extending local connections in the usual manner, whilst the terminals in the tenth level lead to operator's positions for extending calls to manual or automatic main exchanges, each operator's position being accessible over a group of adjacent lines all designated by the same two-digit number. The selector when raised in response to the first digit to one of the first nine levels, automatically hunts over that level in the usual manner to find a trunk leading to an idle connector, but if raised to the tenth level, a cam-operated contact closes a circuit which prevents the automatic hunting-movement and the selector operates in response to the second digit to rotate the wipers on to the first line of the group allotted to the desired operator. If the first line of the group is busy, the selector automatically hunts over the remaining lines of the group in search of an idle line. The P.B.X. subscribers are divided into classes according to the connections to which they are entitled, resistances of different values for each class of subscriber being connected to a fourth wiper of the subscriber's individual line-switches. These resistances control, over a separate conductor extending right through the selector, the energization in an operative cord-circuit of marginal relays which light differently-coloured lamps. Figs. 1 and 2 of the drawing show the setting up of a mainexchange connection, in which the calling subscriber A is connected over his line-switch C and the selector E to a trunk 140, 141, 142 leading to a jack J at an operator's position. The operator extends the connection of a cord-circuit 0 terminating in a plug P<1> which is inserted in a jack J<1> of a trunk leading to a main manual exchange or in a jack J<1> leading to a main automatic exchange. The rotary line-switch C, which is of the no-normal type, has the usual line and cut-off relays combined in one relav 18 provided with a central soft-iron shield 19 and two separate windings 15, 16. Line-switch. When the calling subscriber A removes his receiver, the line winding 16 of the relay 18 energizes and partly operates its armatures 25, 28 so as to close their front contacts, whilst not opening their back contacts. The switching winding 15 is connected in series with the rotary magnet 17 over contact 28, but if the wipers 43 - - 46 are resting on a busy trunk, the switching winding is short-circuited and the rotary magnet operates to rotate the wipers in search of an idle trunk. When an idle trunk leading to an idle selector E is reached, switching winding 15 energizes and acts in conjunction with slow-release line winding 16 to operate all the armatures completely. The calling line is connected through to the selector E at the armatures 23, 30 a moment before the earth connection is broken at armature 28, in order to allow time for a holding ground to be placed on the test conductor 94 at the selector E. Operation of selector E for local connections. When the selector E is connected through to the calling subscriber, line relay 75 energizes and completes the circuit of slow-release relay 74, which puts a holding ground on the test conductor 94 and prepares the circuit of the vertical magnet 83. The impulses corresponding to the first digit of the wanted number are repeated to the vertical magnet 83 in series with the slow-release relay 77 over a circuit 95, 93, 90, 116. Upon the commencement of the vertical movement, the stepping relay 78 is energized in a circuit 106, 100, 123, 94 and locks up over contacts 91, 111, 110, 108, preparing a circuit for the rotary magnet 84. At the end of the series of impulses relay 77 falls back and the rotary magnet 84 is energized over a circuit 103, 110, 123, 94 to rotate the wipers on to the terminals of the first trunk in the selected level. Magnet 84 breaks the locking circuit of the stepping relay 78 which breaks the rotarymagnet circuit at armature 103. If the first trunk is busy, stepping relay 78 energizes over the grounded busy test terminal in a circuit 106, 91, 111, 115, 132, and the wipers are stepped forward under the alternate operation of the stepping relay and the rotary magnet until an idle trunk is reached. Relay 78 does not then energize and switching relay 80 energizes in a circuit 78, 106, 80, 92 to extend the connection to the selected connector which is operated by the remaining impulses to complete the connection in known manner. Operation of selector E for main-exchange connections. It may be supposed that the number of the desired operator is 01. The selector operates in response to the first digit to raise the wipers to the tenth level in which are the groups of lines leading to the operator's positions. When the switch shaft is opposite to the tenth level, contact 107 is closed by means of a cam and relay 79 energizes in a circuit 107, 100, 123, 94 to break the locking circuit of the stepping relay 78 at the armature 110, thus opening the circuit of the rotary magnet and preventing the automatic hunting movement over the selected level. The single impulse coiresponding to the second digit is repeated to the rotary magnet 84 over a circuit 101, 95, 93, 90, 116 to advance the wipers on to the terminals of the first of the group of lines assigned to the wanted operator. Relay 79 energizes in parallel with the rotary magnet 84, but, on this relay falling back, if the first line is busy, stepping relay 78 energizes over the grounded test terminal and the wipers are stepped forward under the alternate operation of the stepping relay and the rotary magnet until an idle line or the last line of the group is reached. The lines in the tenth level are divided into groups by means of the cam 124 which opens the contacts 123 and closes the contacts 122 when the last line of thegroup is reached. The rotary magnet is therefore not further operated, and if this last line is also busy stepping relay 78 energizes and connects the busy tone device T to the upper talking conductor over a circuit 122, 102, 113. If, however, an idle line in the group is reached, switching relay 80 energizes to extend the connection to the jack J at the operator's position. High-resistance relay 201 energizes over the calling-subscriber's line loop in series with relay 200, which does not yet energize, and lights the lamp L. A relay 81 connected in parallel with the condenser in the upper talking conductor energizes in series with the relay 201 and applies a holding ground to maintain the relay 76 energized to prevent the switches C, E from releasing. This arrangement avoids the extension of the release trunk conductor to the operator's position. Extension of connection by operator to main exchange; indicating class of calling subscriber to operator. In response to the lighting of the lamp L, the operator inserts the plug P in the jack J. Relay 213 energizes in series with relay 200 whichalso energizes and extinguishes the lamp L. Relay 214 energizes over the calling-subscriber's loop in series with the relay 200. A fourth wiper 44 of the subscriber's line-switch C is connected to ground over ousbars 33 - - 36 through resistances R, R<1> varying in value according to the connections to which the subscriber is entitled. These resistances determine, over a circuit 39, 44, 114, 131, 141 and the sleeve circuit of the jack. the energization of one or more relays 210, 211. 212 in the cord-circuit, which control the lighting of differently-coloured lamps L<5>, L<6>. The bus-bar 33 of a subscriber entitled to unrestricted service is connected directly to earth and all the relays 210, 211, 212 energize lighting both lamps L<5>, L<6>. For a subscriber entitled only to connections with the main manual exchange, marginal relay 212 does not operate and lamp L<5> only is lit, whilst for a subscriber entitled only to connections to the main automatic exchange, neither of the marginal relays 211, 212 operate and lamp L<5> only is lit. If the subscriber is entitled onlv to local connections his bus-bar 36 is not connected to earth and neither of the lamps L<5>, L<6> are lit, and the subscriber is notified of his non-eligibility by a tone signal over the circuit T<1>, 231, 220 and the lower talking conductor. On learning of the eligibility of the calling-subscriber, the operator depresses her listening key K and enquires the wanted number. If a manual exchange connection is required, the operator inserts the plug P<1> in the jack J<1> of an idle trunk leading to the manual exchange and operates the ringing key K<1>. On the insertion of the plug, relay 216 energizes and completes the circuit of the lamp L<4>, which is extinguished as. soon as the manual operator replies by the operation of the polarized relay 215. If a connection to the main automatic exchange is desired the operator inserts the plug P<1> in the jack J<2> of an idle trunk, connects her impulse transmitter S<1> across the line by means of the key K<2>, and sends sets of impulses corresponding to the wanted number to effect the connection in known manner. When the called subscriber replies, the polarized relay 215 responds and extinguishes the lamp L<4>. Release. When the calling subscriber hangs up, relay 214 relapses and lamp L<1> is lit. Relay 81 also relapses and releases relay 76, which deenergizes relay 80 and completes the circuit 116, 90, 93, for the release magnet 82 which restores the selector to normal. During the release, the test wiper 132 is disconnected from the stepping relay 78, thus preventing the latter from energizing when a busy set of terminals is passed and so interfering with the release. When the called subscriber han