Patent GB-222502-A (GB)
Title: Improvements in telephone exchange systems
IPC: H04Q3/00
Filed: 1924-09-26
Abstract: 222,502. Western Electric Co., Ltd., (Assignees of Williams, S. B.). Sept. 26, 1923, [Convention date]. Automatic exchange systems; party-line systems.-In a system in which the dialled number is received by an impulse recorder which afterwards transfers it to a marker, two markers are provided which are taken into use alternately for successive calls. If either marker is defective, all calls are forwarded to the other. Each marker is accessible to all the impulse recorders and is capable of controlling all the numerical switching apparatus in the exchange, which is of 4-digit capacity in the example described. All testing operations to find idle trunks and links of desired numerical groups and the test of the idle or busy condition of the wanted line are conducted in the markers, which are also designed to control the selective ringing of 4-party lines. In the system described, a connection is completed through a non-numerical switch 100, Fig. 1, a group selector 300, Fig. 3, and a connector 400, Fig. 4, all of cross-bar type with link circuits (shown horizontally) for connecting incoming and outgoing lines and trunks (shown vertically). In a switch of this type, two marking magnets are temporarily energized to mark appropriate incoming and outgoing vertical rows and a link magnet is then energized to complete and maintain the connection. Subsequent but concurrent calls may be switched through other links of the same switch. The links in each switch are divided into groups. In the connector 400, for example, there are ten groups of links corresponding to different units digits of wanted lines, so that an idle link must be chosen of a group determined by the units digit. There is a single connector in each primary numerical division of the exchange, and all the trunks to it are multipled in all the group selectors, where they appear in the contacts of that part of a particular outgoing vertical row which belongs to a particular group of links. Thus in a group selector, after the appropriate incoming and outgoing vertical rows have been marked, a link must be chosen which belongs to a particular group and is idle itself and has access to an idle trunk over the marked outgoing row. Each incoming trunk in the group selector, and also in the connector, occupies a complete vertical row, such as 310, 410, and therefore has access to all links. A trunk such as 121, Fig. 1, seized by the non-numerical switch 100 is connected laterally by a similar switch 600, Fig. 6, to an idle impulse recorder shown in Figs. 7 and 8, which records the wanted number and transfers it over wires 910, Fig. 9, to one of the markers, such as that shown in Figs. 11, 12 and 13. A set of relays shown in Fig. 10 controls the alternate use of the markers and locks a defective marker out of action. The impulse recorder and marker are released as soon as the connection is completed, and ringing and talking current are supplied from the repeater shown in Fig. 2, which, in the case of party-line calls, can supply either single or double rings on either the a or b wire. In the case of reverting calls the selector 300 switches the calling line direct to a selective ring-back equipment such as is shown in Fig. 5. Description will first be given of the extension of a call to a non-party line 2132, Fig. 4. It should be noted that the first digit of a reference numeral generally corresponds with the figure in which it occurs. Connection of calling line 101, Fig. 1, to idle trunk 121 by cross-bar switch 100. Each subscriber occupies part of a vertical row such as 110 and has access to a group of links such as 130, 140, &c. All the groups of links have access in common to the outgoing trunks such as 121. The vertical row containing the calling line is marked by energizing a magnet 113, controlled by a set of relays 104, 105, 108 common to all the calling lines in that row, and the outgoing vertical row belonging to an idle trunk 121 (picked out by an allotting switch 115) is marked by energizing a magnet 114. The operating magnet 144, 132, &c. of an idle link of the group 130, 140, &c. to which the calling line has access is then energized to complete the connection, and the marking magnets 113, 114 are released. The link-operating circuit is closed bv a relav 126 common to all the calling lines served by that group of links, and is extended to the magnet of the first idle link in the group through contacts of busy relays 133, 134, &c. The operations in detail are as follows : Line relay 102 energizes 104, which energizes 108, 102. Relay 108 energizes 105 (which cuts out 104 and locks 112) and locks itself in series with 109, which energizes 125 and the marking magnets 113, 114. Magnet 114 locks itself in series with relay 111 (which for the moment is short-circuited) and grounds wire 124 to advance the switch 115 to the next idle trunk. During this movement relay 119 is energized and takes the short-circuit off 111, which open-circuits the sluggish relay 125. Meanwhile magnet 113 has closed a circuit for relay 126, which locks itself in series with 128 and completes a circuit (assuming that the first link 130 is idle) for magnet 144, which locks itself in series with 133, 131, and the cutoff relay 103 is energized in a branch of the locking circuit. The relapse of relay 125 unlocks 108, 109, 105, 113, 114, 111 and the equipment is in condition to switch the next call. Connection of trunk 121 to idle impulse recorder 7, 8, by cross-bar switch 600, Fig. 6. This operation is exactly similar to that described in the preceding paragraph. It is started by the energization over circuit 124 of relay 602, which locks itself over circuit 236 and energizes 230 to keep the circuit 124 grounded. Marking magnets 613, 614 are energized and then an operating magnet 631, which locks to wire 624 and switches a lateral branch of the trunk 121 through an idle link 630 to the leads 121 of an idle impulse recorder. Relay 204, energized in a branch 234 of circuit 624, connects wires 122, 123 to 232, 233, locks 203, and de-energizes 602. Operation of the four-digit impulse recorder, Figs. 7 and 8. Each digit is recorded by energizing a particular combination of relays in the sets Th, H, T, U, Fig. 8. Each set consists of four relays which are connected, one set after another, to four code wires 721 - - 724 controlled by a relay counting chain 701 - - 706. This counting chain, which comprises only six relays, is so arranged that impulses up to five repeated over the righthand contact of relay 712 cause the successive energization of relays 701 - - 705, each relay unlocking its predecessor so that only one relay remains energized at the termination of the digit. The relay 705, however, locks itself independently of the other relays of the chain, and subsequent impulses energize relays 701 - - 704 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 721 - - 724 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. Relay 700 is energized over the calling loop and energizes 709, 710 to ground the wire 624, to energize relay 717, and to complete a dialling tone circuit 753 through a repeater coil 713. The relapse of relay 700 at each dialled impulse removes a short-circuit from relay 711, which energizes 712, which connects itself to the first counting relay 701. At the termination of the impulse, when ground is removed from the right-hand contact of 712, relay 701 becomes energized in series with 712, and the decrease of current in the right-hand winding of relay 712 causes it immediately to relapse, this being assisted by an opposing current in its lefthand winding. Relay 701 locks itself in the circuit 750, 730 and prepares 702 for operation by the next impulse. Relay 702 then locks itself and prepares 703, and so on. A relay 718 is energized by 711 and locks itself, so that the sluggish relay 717 is dependent during the digit on the current it receives intermittently from 711. At the termination of the digit the relay 717 relapses and grounds wire 751 to energize relay 811, which connects the thousands relays to the code wires 721 - - 724. The energized register relays lock themselves to wire 830 and energize relay 812, which also locks itself and energizes 861. Relay 812 disconnects the grounded wire 751 from 811, which remains energized over wire 752 in series with 719. Relay 719 disconnects the wire 750 to unlock the counting relays and de-energizes relay 718, which in turn opens the circuit 752 of relays 719, 811, and relay 717 again becomes energized. The remaining digits are counted and stored in the same way, relays 821, 831, 841 being energized at the termination of the respective digits to connect the proper register relays to the code wires. Connection of impulse recorder to one or other marker. Connection is made between impulse recorders and markers over a single set of wires 910, Fig. 9, common to all the impulse recorders and to both markers. The wires from the impulse recorder shown in Fig. 8 are connected to the wires 910 by a relay 913, and similar relays such as 916 connect other impuise recorders. The circuits at the foot of Fig. 9 ensure that only one of these relays shall be energized at a time, i.e. that only one call shall be marked at a time. The wires 910 can be connected to the marker shown in Figs. 11, 12, and 13 by relay 930 or to a second marker (not shown) by a similar relay. The circuits shown in Fig. 10 are common to both markers and ensure (inter alia) that the two markers shall be taken into use alternately. Accordingly as