Patent GB-190626301-A (GB)
Title: An Improved Automatic Telephone District System and Means for use in Automatic Telephony.
Inventor: JAMES REGINALD WILLIAM
Filed: 1906-11-20
Granted: 1907-11-20
Abstract: 26,301. James, R. W., [Automatic Electric Co.]. Nov. 20. Telephone systems.-Relates to automatic telephone systems in which the subscribers' lines in various districts terminate at auxiliary or subcentral stations, through which no communications can be directly established but which serve to establish connexion with a central or main trunking station. The subscriber's individual switch at the sub-central station serves to pick out a disengaged trunk line to the central station, and all the individual switches at one station are controlled by a master switch, which maintains all the dis. engaged switches in readiness to make connexion with a disengaged trunk. In addition to the individual switches, the connector switches are located at the sub-central stations, the selector switches being at the central station. The trunk lines from the sub-centrals to central. consist of two conductors only, provision for release being obtained by the use of repeaters at the sub-centrals for the incoming trunk lines, and repeaters at the central for the outgoing trunk lines to the connectors, these repeaters transmitting the switchoperating impulses as well as the voice currents. The common battery supply of current to the speaking-circuits is supplied through the connector, no current for speaking purposes being supplied until the called subscriber has responded. During conversation the common battery is switched into a bridge in series between the two line relays of the connector, together with a differential relay for controlling the release. Figs. 20, 21, and 22, which are to be read in conjunction, show a, talking - circuit established between a calling subscriber 1122 and a called subscriber 2211. The reference letter A denotes the individual switch of the calling subscriber at sub-central ; H the master switch controlling the individual switches ; C the repeater to the trunk line 374, 379 ; D the first selector at central ; E the second selector ; C' the repeater to the outgoing trunk line 431, 435 ; F the connector at sub-central, which selects the called subscriber's line in accordance with the current impulses that represent the last two digits of the called subscriber's number. The called subscriber's individual switch is indicated at A'. Each subscriber's line is normally short-circuited through contact-springs 37, 38, Fig. 1, the short-circuit being removed when the cut-off relay 5 is energized. The normal short-circuit keeps the cables free from inductive disturbances, and gives a quiet line service. Indivdiual switch. When the calling subscriber removes his receiver from the hook, a momentary ground is put on the "rotary" side 351 of the line by a passing contact made at 160, 161. The effect of this is to energize the trip magnet 6 of the subscriber's individual switch at the sub-central station, the circuit passing through the springs 38, 37, 36 of the cut-off relay 5. The individual switch and cut-off relay are shown in Fig. 1. The armature 16 of the trip magnet 6 is pivoted at 18 to the armature 13 of the switchrelease magnet 7. When the armature 16 is attracted, the detent 26 releases the plunger arm 4, and the spring 27 forces the plunger 3 into the bank of contacts Q. The position of all the idle switch plungers 3 at any instant is determined by the angular position of a recessed shaft 25 of the " master switch " at the sub-central, for the angular position of a plunger 3, quitting the bank Q after a conversation is concluded, is brought into agreement with that:of all the other idle plungers by the action of the nose 3<a> in fitting itself into the recess in the shaft 25. As will be subsequently explained, the master switch is actuated after any individual switch has been brought into use, so as to bring all the idle plungers 3 into a position to make use of a disengaged portion of the bank Q. The function of the plunger 3 is to expand certain contact-springs, so as to connect the calling subscriber's line with a disengaged trunk line proceeding to the central station. These trunk lines, which are much smaller in number than the subscribers' lines, are multipled on the banks Q of the individual switches, and as each line is rendered " busy," the master switch is set in action to move the remaining idle plungers 3. The plunger 3, in addition to establishing connexion between the line contact-springs 371, 376, Fig. 20, and the trunk contact-springs 372, 377 also closes the contact-springs 361, 362 in the circuit of the release magnet 7, and earths at 357, 358 the wire 354 leading to the private bank contacts of the calling subscriber's line multipled on the connector switches at the sub-central station, so that the calling subscriber's line is rendered " busy against attempted calls. The ground at 357, 358 also establishes a circuit from the main battery wire 350 through the cut-off relay 5 to earth, and thus removes the short-circuit from the calling subscriber's line. Master switch. The master switch which controls the rock-shaft 25 is actuated by a motor magnet 61, Fig. 20, with a self-acting make-and-break device 91. Each time the armature 81 of the motor magnet is attracted, a ratchet-wheel is caused to move through the distance of one tooth, and by the action of a pin on a cam-shaped lever, the contactarm 67 and shaft 25 of the master switch are shifted one step. At the end of its step-by-step travel to the left, the arm 67 returns in a single step to its starting point, the shaft 25 and idle plungers 3 making a corresponding movement. The calling subscriber in Fig. 20 having seized upon an idle trunk line which corresponds to the extreme right-hand contact-point 110 of the master switch, a guarding-potential is established at that point via the contacts 362, 361 and release magnet 7. The contact-arm 67 being on the point 110 at the time of the call, a circuit is established through the windings 124, 120 of the relays 62, 63. The consequent energization of the relay 63 effects the closing of the circuit of the motor magnet 61, and the master switch commences its automatic step-by-step movement, which continues as long as the contact-arm 67 finds guarded contact-points, corresponding to engaged trunk lines. Repeater. The repeater C at the sub-central station comprises "vertical" and "rotary" line relays 163<c>, 164<c>, repeating-coils 172<c>, 173<c>, and condensers 170<c>, 171<c>. Among the contact-springs controlled by the line relays are the trunk-release springs 165‹, 166<c>, which are brought into contact when the vertical and rotary sides of the line are simultaneously grounded. The continuity of one side 379 of the trunk line 379, 374 is controlled by a differential relay 178<c> at the springs 179<c>, 180<c>, which relay by breaking the normal bridge through the pole-changing relay 190<c> prevents impulses intended for one side of the line from reaching the other. The supply of talking-current to the calling subscriber's line takes place on the one side through the winding 181<c> and vertical line relay 163<c>, and on the other side through the rotary line relay 164<c> and winding 182<c>, the windings 181<c> and 182<c> being in opposition ; but as the bridge containing the battery includes the ground at 191<c>, the talking-current is not supplied to the line until the pole-changing 'relay 190<c> is energized. This does not take place until the called subscriber replies. First selector. The calling subscriber having established connexion in the manner described above with a first selector D at central through the trunk line 374, 379 by the preliminary act of removing his receiver from the hook, he then proceeds to press the " vertical " button 130 the requisite number of times for each digit of the called subscriber's number, following each such series of depressions with a single depression of the rotary button 131. In the example shown in the Figures, the number of the called subscriber is taken as 2211. The first double depression of the button 130 earths the line 345 twice, and energizes twice the vertical line relay 163<c>. In consequence, the conductor 375 and vertical trunk line 374 are earthed twice through the contact-spring 187<c>, and the vertical line relay 188 of the first selector D is energized twice, for the " side-switch " arm 257 is at this time on its first contact point 263. The lioe relay 188 closes the circuit of the battery B through the vertical magnet 199 and the springs 240, 241 of the " private magnet 235, and in consequence the shaft of the first selector is raised two steps so as to bring its contact-arms on to the second level of its bank of contacts. The depression of the rotary button 131, which follows the double depression of the button 130 corresponding to the first digit of the called subscriber's number, energizes the rotary line relay 164<c> of the repeater C, and thereby earths the rotary trunk conductor 379 and energizes the rotary relay 189 of the first selector. The relay 189 controls the private magnet 235, which attracts and releases its armature, thereby allowing the escapement arm of the side switch to move through the first of two steps, and causing the four switch arms 255, 256, 257, 258 to move on to their second contact-points. The ground thus effected at G<7> causes the energization of the rotary magnet 222, which is provided with an automatic make- and-break device 232, 233. The first rotary movement of the selector shaft due to the action of the rotary magnet brings the wiper arms of the selector on to the first contact in the second level already selected. There is a mechanical relation between the armature of the rotary magnet and that of the private magnet, such that each time the rotary magnet is energized, the armature of the private magnet is forced against its pole-piece. The private magnet, however, controls the escapement of the side switch, so that a second double movement of its armature would carry the s