Patent GB-191229351-A (GB)
Title: Improvements in or relating to Telephone Systems.
Filed: 1912-12-20
Granted: 1913-12-22
Abstract: 29,351. Automatic Telephone Manufacturing Co., [Automatic Electric Co.]. Dec. 20. Automatic and semi-automatic exchange systems; metering-systems.-Relates to districtoffice and like systems in which the subscribers are connected to sub-offices, connected by trunks to their respective main offices, the object of the invention being to enable connexions between two subscribers on the same sub-office to be completed without tieing up trunks to and from the main office. This is effected by inserting, at the sub-office, in each connexion, a kind of selectorrepeater, which for calls extending through the main office functions as a repeater only, but for local connexions functions as a selective switch for connecting the calling line to a group selector or connector, and also breaks down the connexion to the main exchange. In the system shown in Figs. 3, 4, and 7, the selector-repeater L' is arranged between the bank contacts of line switches E' and secondary switches H', having access to trunks leading to group selectors I' at the main exchange. The selectorrepeater L' is provided with a set of wipers 35, 36, 37, 38, 39, positioned by the vertical and rotary magnets 40, 41 in the usual way, but provided with contacts in one level only, certain of these contacts leading to secondary switches M<1>, Fig. 7, which extend connexion to group selectors or connectors suitable for establishing local connexions. Assuming that the subscribers connected to a certain sub-office are numbered from 11,100 to 11,299, the selector-repeater extends a calling line to a local connector only when the first three sets of selecting-impulses correspond to the digits 1, 1, 1 or 1, 1, 2. The wipers 35 ... 39 engage bank contacts in their first level only, and the first contact in this level, corresponding to the thousands digit, is connected to a relay 43 which locks the side-switch in its second position, so that the rotary magnet receives the impulses corresponding to the hundreds digit. When a connexion is made through the main exchange, the wipers 35 ... 39 are operated by the first two sets of impulses, but without producing any effect. It will be convenient to describe first the method of establishing a connexion through the main exchange and then one through the sub-office only. Connexion through main exchange. Primary and secondary line switches. When a subscriber T' removes his receiver, his line-switch E' connects him to a selector-repeater, the line relay 33 of which is energized over the springs of a reversing-relay 34 and the calling line. The line-switch E<1> and master-switch N operate as described in Specifications 1421/10 and 15,072/12 respectively. The relay 33 energizes a slow-release relay 48, which by grounding its spring 93 energizes the pull-down winding 99, Fig. 4, of the secondary line-switch H' over lead 32 and contact 98 of relay 47, thus extending the call to a first selector I<1> at the main exchange. The line relay 109 of the selector is energized over lead 30, the upper winding of the reversing-relay 34, the upper winding of a relay 112, contact 111 of the line relay 33, and the lead 31. If all the trunks to the main exchange are engaged, this circuit is not completed, and the relay 112 permits the connexion of the special busy generator Q to the calling line. Selector-repeater. The first set of selecting- impulses is repeated by the relay 33 (1) to the vertical magnet 40 and private-magnet relay 49, connected in parallel therewith, and (2) to the group selector I<1>, by the opening and closing of contact 111, the upper windings of the relays 34, 112 being short-circuited by the relay 49. When the impulses cease, the relay 49 deenergizes the private magnet 45, which moves the side-switch arm 44 into its second position, and the group selector I<1> extends the call to a further group selector in known manner. The second set of selecting-impulses is repeated to the rotary magnet 41 and to the second selector, after which the side-switch arm 44 passes to its third position, and the second selector finds an idle third selector. The wipers of the selectorrepeater have been moved by these sets of impulses to an inoperative position, since the wanted connexion is to be made through the main exchange. Selectors and connector. The group selectors and connector operate to find, and ring up, the wanted line in the manner described in Specification 1298/10. Metering calls. During the establishment of a call, the currents through the windings of the meter magnet 27 oppose each other, but when the called subscriber answers, a relay at the connector reverses the current flowing over the leads 30, 31, and the upper winding of the reversing-relay 34, which in turn reverses the current through the left-hand winding of the meter magnet. Release. When the calling subscriber hangs up, the relays 33, 48 de-energize, and the latter opens the circuit of a relay 118, controlling the release magnet 46. The opening of the contact 111 also brings about the release of the group selectors and connector. Connexion through local exchange. It is assumed that subscriber No. 11,110 wishes to call subscriber 11,225 on the same sub-office. When he removes his receiver, the switch E', selector-repeater L<1>, and secondary line-switch H<1> operate as before to connect him to a first selector I<1> at the main exchange. The first digit impulse, as before, raises the selectors I<1>, L<1> to their first level, this being the only operative level for the switch L'. The second digit impulse operates the second selector at the main exchange and also rotates the selector-repeater one step, whereby the wiper 38 is brought to rest upon a contact connected to the upper winding of a relay 43, which energizes in series with the private magnet 45, thus locking the side-switch in its second position. The relay 43 completes a locking circuit through its lower winding, and contacts 169, 92 to ground G', and by closing contact 171 grounds certain contacts 173, 174 in the path of the wiper 39. These contacts are displaced from the contact on which the selector is positioned by the thousands impulses by a number of steps equal to the value of the hundreds digits of the lines connected; for example, if the sub-office serves the lines 11,100-11,299, the selector is arrested by the thousands impulses on the first contact of the first (and only) level, and the relay 43 grounds the second and third contacts 173, 174 in this level. The third set of selecting-impulses operates the third selector at the main exchange, and also further rotates the selector L', and since the hundreds digit of the wanted line is 2, the wipers 35 ... 39 come to rest upon the third set of contacts 174 ... 178, of which the contacts 175, 176, 177 are connected to a secondary line-switch M<1>, Fig. 7, which extenas connexion to a connector serving the lines 11,200-11,299. The engagement of the wiper 39 with the grounded contact 174 energizes the switching-relay 47, which extends the calling line to the wipers 35, 36, secondary line-switch M<1>, and connector. The relay 47 also disconnects the line relay 33, which opens contact 111, thus releasing the group selectors at the main exchange. The opening of contact 98 by the relay 47 also releases the line-switch H', Fig. 4. The relays 43, 118 are, however, kept energized by the grounding of the lead 242 at the local connector. The fourth and fifth sets of impulses position this connector in the usual way. When the calling subscriber hangs up, the connector removes the ground on the lead 242, and the relay 118 closes the circuit of the release magnet 46. If an entire thousand subscribers in a fivedigit system are allotted to the sub-office, the connexion can be switched to the local switches as soon as the second digit is called; in this case the wiper 38 and the locking-relay 43 are not required, and the call is switched to a group selector instead of direct to a connector. If all the numbers which begin with a certain digit are allotted to one sub-office, the connexion can be switched to the local selectors when only one digit is called, and in this case the selectorrepeater can have a rotary movement only, the vertical magnet being dispensed with. Specification 1423/10 is also referred to.