Patent GB-213668-A (GB)
Abstract: 213,668. Automatic Telephone Manufacturing Co., Ltd., (Automatic Electric Co.). Jan. 4, 1923. Addition to 211,189. Automatic exchange systems.-Relates to systems of the kind described in the parent Specification, in which two or more exchanges, accessible over different routes, are called by dialling the same initial digit or digits, and in which, when the initial digit does not determine definitely to which exchange the call is to be extended, a trunk is seized to each exchange to whch the call might go, the trunks not required being released as soon as the wanted route has been finally determined. According to the present invention, the first selector has two or more sets of wipers, which select idle trunks for the two or more routes. A digit registering device, provided at the point at which the routes diverge, responds to the second and third digits and determines over which route the call is to be completed, or in the case of calls to an exchange in the same district, or to a line on the calling exchange, extends the call to a local fourth selector over a circuit which does not include the wipers of the first selector, the use of second and third selectors being thus avoided for local calls. General arrangement. The invention is described as applied to a network of exchanges divided into three districts A, B, C, Figs. 1 and 4, the main exchanges D, E, F in each district being connected to an exchange in every other district and to each of the main exchanges in its own district. A calling subscriber A<7>, Fig. 4, on exchange E is connected to an idle selector-repeater 1E, the two sets of wipers of which have access on the 5th level through rotary line switches C<1>, C<2> to trunks leading to main exchanges D, F, respectively. If the subscriber dials K, L or M as the first character of the wanted exchange, (as when calling exchange LARabee, LOMbard, MABurn, or MAIn), both sets of wipers are raised to the 5th level and rotate to find idle lines which are extended by rotary line switches C<1>, C<2> to idle trunks leading to second selectors 2E<1>, 2E at exchanges D. F. The impulses corresponding to the second character dialled, say A, operate the selectors 2E, 2E', and the digit register SD. The impulses oorresponding to the third character operate the selectors 3E, 3E', and the register SD. If the second and third characters determine the selection of an exchange in district C such as F or G, the register SD restores switch C' and the trunk leading to exchange D. Similarly, if the wanted exchange is K in district A, switch C<2> and the trunk leading to exchange F are restored. If the wanted exchange L is in the same district as the calling exchange, the register SD releases both switches C<1>, C<2> and extends the call over line switch C<4> to exchange L, the first three digits being in effect suppressed. If the calling subscriber dials the character G (as when calling exchange GROve), the wipers of the selector-repeater are raised to their 4th level, the trunks from which may be combined with those in the 5th level since there is no exchange in the district A having a second letter in the same hole on the dial as the letter R. The selectors 2E<1>, 3E<1> in exchange D are raised to the 7th and 10th levels respectively and extend the call to the fourth selector 4E<4>. A single group of third selectors 3E<1> may handle calls to both the GROve and MABurn exchanges, since there is no conflict in the third digit for any exchange in this district. Finally, if the wanted line is in the calling exchange CEXtre, the wipers of the selector-repeater are rotated over the second level, which is dead, and the register SD responds to the 2nd and 3rd digits and causes the line switch C<3> to extend the call to a 4th selector 4E<2> in the same exchange, the first three digits being suppressed. Selector-repeater and digit register, Figs. 5 and 9. The selector has two sets of wipers 120 - - 122 and 124 - - 126, and is associated with a digit register SD, which structurally resembles a Strowger connector, responds to the second and third digits, and selectively energizes one or more of the four switching relays 52, 53. 54, 55 whereby the repeater may be extended (1) over switch C<4> to a local exchange, (2) over switch C<3> to a fourth selector in the same exchange, (3) over wipers 124 - - 126 and switch C<2> to the MAIn exchange, Fig. 7, or (4) over wipers 120 - - 122 and switch C<1>, Fig. 6, to the GROve exchange. A calling line A<10>, Fig. 5, is connected by its line switch C<10> to an idle selector-repeater, the line and release relays 56, 57 being energized as usual. The wipers are raised to the required level, say the 5th, and are rotated until both sets of wipers simultaneously engage with idle trunks, whereupon the switching relay 60 closes a bridge across the wipers 120, 122 and 124, 126 through contacts of the line relay 56 and completes circuits over the test wipers 121, 125 for the line relays 201, 241 of the switches C<1>, C<2>, Fig. 6, which extend the repeater over two-wire trunks to second selectors, such as 2E, Fig. 7, in the two distant exchanges. Call to LARabee exchange (5, 1, 7) through selectors 2E, 3E, and repeater R at MAIn exchange. The 2nd and 3rd characters dialled operate in the usual way selectors 2E, 3E, Fig. 7, at the MAIn exchange, and similar selectors at the GROve exchange. These impulses are also repeated by the line relay 56 over wire 150 to the vertical and rotary magnets 506, 505 of the digit register SD, Fig. 9, causing the wiper 520 to engage contact 17 (corresponding to the characters AR). As soon as the impulses through the rotary magnet 505 cease, a circuit is closed through the switching relay 54, contact 17 of switch SD, wiper 520, contact 71 (closed by a cam on the selector shaft when raised to its fifth level), relay 501, to earth. Relay 501 prevents the digit register from being operated by subsequent impulses. The switching relay 54 locks up, opens the circuit over the test wiper 121 for the line switch C' which releases the trunk to the GROve exchange, and connects the repeater tothe wipers 124, 126 over contact 88 of the line relay. The selector 3E, Fig. 7, having selected a repeater R leading to the LARabee exchange, successive sets of impulses are repeated by relays 56, 370 to operate selectors to select, test, and ring the wanted line in the usual way. The connection is released when the calling subscriber replaces his receiver. Call to MAIn exchange (5, 1, 1). This proceeds as in the previous paragraph, except that the switching relay 54 is energized over contact 11, instead of contact 17, and that selector 3E, Fig. 7, selects a local selector 4E<1> instead of a repeater R. Call to MABurn exchange (5, 1, 2) through selectors 2E<1>, 3E<1> and repeater R<2> at GROve exchange. This proceeds like the call to LARabee exchange, except that the switching relay 55 (instead of relay 54) is energized over contact 12 of the digit register, and locks up, opens the circuit over the test wiper 125 for the line switch C<2> which releases the trunk to the MAIn exchange, and connects the repeater to the wipers 120, 122 over contact 88 of the line relay 56. Calls to LOMbard exchange (5, 10, 5) in same district as calling exchange. This proceeds as before, trunks to the GROve and MAIn exchanges being taken into use over the 5th level of the selector repeater. In this case, however, both the switching relays 54, 55 are energized over the contacts 05 of the digit register to release the trunks to the GROve and MAIn exchanges and in addition a relay 52 is energized over wiper 521 of the digit register, thereby switching the repeater through to a line switch C<4> which extends the call direct to a 4th selector in the LOMbard exchange. Calls to lines on the calling exchange CENtre (2, 3, 6). In this case the wipers are raised to the second level, which is dead, and rotate to the first terminals without effect. The 2nd and 3rd digit impulses pass only to the digit register. Both the relays 54, 55 are energized over wiper 520, and the relay 53, energized over contact 36 engaged by wiper 521, extends the repeater over switch C<3> to a local 4th selector. Calls to GROve exchange (4, 7, 0). In this case, the wipers are raised to the 4th level, the terminals engaged by the lower set of wipers being dead. The terminals of the 4th level engaged by the upper wipers are multipled to the 5th level, as there is no conflict between the second character in the exchanges in district A. The wipers of the digit register engage contacts 70; that engaged by wiper 520 is dead, but that engaged by wiper 521, like all similar contacts having no switching function, is connected by lead 525 to relays 55, 501, which operate as before described.