Patent GB-231548-A (GB)
Abstract: 231,548. Western Electric Co., Ltd., (Western Electric Co., Inc.). Nov. 6, 1923. Automatic exchange systems.-The designation of a wanted line is registered on an impulse recorder which afterwards successively transfers portions of it to markers at the various switching stages, the impulse recorder being connected to the markers over means independent of the talking connection. The connecting switches are divided into groups, to each of which are allotted a number of impulse recorders and a common marker. All the testing operations to find idle trunks and links of the desired numerical groups, and the test of the wanted line, are conducted in the markers. Busy current is supplied from the impulse recorder. The invention is described with reference to a system in which all the switches are cross-bar switches of the kind described in Specification 183,438, in which incoming lines are connected to outgoing trunks through link circuits, the connection over a link circuit being held by the link-operating magnet after the in- and out-marking magnets have been released and rendered available for completing further coexisting connections over other idle link circuits. In the system illustrated. Figs. 1 to 13, when arranged as indicated in Fig. 16, form a single circuit diagram. With a few exceptions the hundreds digits of a reference numeral indicates the figure in which it is to be found. A calling line is extended by a line switch 100, Fig. 1, to an idle first selector trunk 114 pre-selected by an allotter 143. A branch of the trunk 114 is connected to an impulse-recorder finder 600, Fig. 6, which extends the calling line to an idle impulse-recorder, Figs. 7 and 8, preselected by an allotter 626. The wanted number is recorded on thousands, hundreds, tens, and units registers 800 - - 803, Fig. 8, and as soon as the thousands register 800 is set, the impulse recorder is connected over a multi-contact relay group 900, Fig. 9, to the common section marker, which marks a group of trunks to the wanted exchange section and makes a double test for an idle trunk, such as the trunk 350, associated with an idle link 307, causes the selector 300 to extend the trunk 114 to the selected trunk 350, and then releases itself for further use. A line marker. Figs. 11 and 12, serving the wanted exchange section, is then associated with the impulse-recorder over a multicontact relay group 1101, and the hundreds, tens, and units records on the registers 801 - - 803 are transferred to marking relay groups 1200, 1202, 1201, Fig. 12, respectively. Since the subscribers' lines are arranged in two-thousand line groups, translation is involved; this is effected at the line-marker, Figs. 11 and 12. In accordance with the setting of this marker, the wanted line is picked out in the connector 500, Fig. 5, in which it appears, and a double test is made for an idle trunk, such as the trunk 422 to this connector, also associated with an idle second selector link 405, Fig. 4. The wanted line is then tested over an auxiliary link 509. If it is busy, the calling subscriber is given a busy signal from a busy current source located at the impulserecorder, and the line marker, Figs. 11 and 12, is dissociated from the impulse-recorder. but if the called line is idle, the trunk 350 is extended over the link 405 to the selected trunk 422, which in turn is connected over an idle connector link, such as the link 508, to the wanted line. The impulse-recorder and the marker are then released. When the lines of a system comprise different classes, such as flat rate lines, message rate lines, and coin-box lines, groups of line switches are allotted to each class. The trunks from the line switches may be distributed in the groups of first selectors in any arbitrary manner to meet varied traffic requirements. Some of the trunks outgoing from the first selectors may lead to other exchanges. Private branch exchange lines are allotted a call-line located in a connector in a position corresponding to the numerical designation of the P.B.X., but the P.B.X. trunks themselves may appear indiscriminately in any number of connectors. When the P.B.X. member is called, a connection is first built up to the call-line, over which a relay is energized to initiate the selection of an idle P.B.X. trunk. An idle trunk having been picked out, the connection from the second group selector to the call line is released, and another connection to the selected P.B.X. trunk automatically established. Line switch 100, Fig. 1. Assuming that the subscriber 101 desires connection with the line 535, the directory number of which is 1234, on removing his receiver, the line relay 121 is energized and completes a circuit for a relay 129, which, together with relays 128, 130, is common to the vertical row of contacts 110 in which the calling line terminates. The relay 129 closes circuits for relays 130, 131, the former locking up over its right-hand winding in series with a relay 135, which energizes a slow-release relay 136 and completes circuits for the in-marking and out-marking magnets 116, 118. The magnet 116 prepares the contacts in the incoming vertical row 110, and energizes a relay 122 common to the Jinks 106, 107 connectable to the calling line, whilst the magnet 118 locks up over conductor 160, energizes a trunk relay 146, and prepares the contacts in an outgoing vertical row 112 allotted to an idle outgoing trunk 114 preselected by the allotting switch 143. The relay 122 locks up in series with a relay 134, and the relay 146 closes a self-interrupting circuit for the driving magnet 138 of the allotting switch 143. which steps round to find the next idle trunk. Directly the switch 143 leaves the 'position shown, a shunt is removed from the relay 137, which energizes in series with the magnet 118 and de-energizes the slow-release relay 136, which, however. holds the relays 130, 135 energized sufficiently long for the calling line to be extended over an idle link in the following manner. Assuming the first link 107 is idle, the relav 137 closes a circuit for the link-operating magnet 125, which effects a connection between the calling line and the trunk 114. Immediately this connection is established, a temporary holding circuit is closed for the magnet 125, in series with the link-busy relay 127, over the third wire of the link. and a parallel circuit is completed for the cut-off relay 120, which de-energizes the line relay 121. Simultaneous calls. The relay 130 when first energized closed a circuit for a relay 128, which locked up over contacts of the relay 131 and opened the circuit of the vertical group relay 129. Should another line in the same incoming vertical row as the subscriber 101 attempt simultaneously to make a call while a subscriber in a succeeding vertical row is calling, the relay 131 is held energized over the contact of another line relay, the locking circuit of the relay 128 is preserved and the re-energization of the relay 129 is prevented. When, however, all simultaneous calls in subsequent groups have been handled by the line switch, a, series circuit is closed for a slow-release relay 132 through the back contacts of all relays similar to relay 129, and the relay 132 energizes and unlocks relav 128. Impulse-recorder selector 600. Fig. 6. This comprises a cross-bar switch the incoming and outgoing lines of which are similarly arranged to those of the line switch 100, Fig. 1. The trunk relay 146 extends ground over conductors 150, 206, to a line relay 613, which operates similarly to the relay 120 of the line switch and causes in-marking and out-marking magnets 629, 631 and a link operating magnet 610 to energize and extend a branch of the seized first selector trunk 114 over an idle link 607 to a group of conductors 632 leading to an idle impulse-recorder preselected by an allotting switch 626. The line relay 613 also energizes a relay 204, which applies holding ground to the conductor 150, whereby link magnet 125 and relays 127, 120, 146 are maintained energized after the deenergization of the in- and out-marking magnets 116, 118, which occurs on the relapse of the slowrelease relay 136. Immediately the connection is established-through the selector 600, a circuit is closed for a relav 2C1, which, extends the calling line to the impulse relay 700 of the impulse-recorder, and closes a locking circuit for the holding relay 204. Impulse-recorder, Figs. 7 and 8. Each digit is recorded by energizing a particular combination of relays in the sets 800, 801, 802, 803, Fig. 8. Each set consists of four relays which are connected, one set after another, to four code wires 729, 730, &c. controlled by a relay counting chain 712 - - 717. This counting chain, which comprises only six relays, is so arranged that impulses up to five cause the successive energization of relays 712 - - 716, each relay unlocking its predecessor so that only one relay remains energized at the termination of the digit. The relay 716, however, locks itself independently of the other relays of the chain and subsequent impulses energize relays 712 - - 715 a second time, so that for digits above 6 one of these relays is energized along with 705. Moreover, for digits above 6 a relay 706 is also energized. Thus either a single relay or a combination of several relays is energized according to the value of the dialled digit, and the code wires 729, 730, &c. are connected through armatures of the relays in such a manner that they are marked in a different combination for each value of the digit. The operations in detail are as follows. The impulse relay 700 energizes a slow-release relay 702, which energizes a slow-release relay 706 and grounds the holding wire 638 to hold the link magnet 610 of the impulse-recorder selector 60u after the de-energization of the in- and outmarking magnets 629, 631, which takes place in the same mann