Patent GB-190504716-A (GB)
Title: Telephone Exchanges.
Inventor: LUNDQUIST FRANK ALBERT
Filed: 1905-03-07
Granted: 1905-06-08
Abstract: 4716. Lundquist, F. A. March 7. Telephone systems.-An automatic exchange consists of two sets of switches, known as main and auxiliary, there being about ten times as many main switches as there are auxiliary switches. The principal difference between these two sets of switches is that each of the latter has a third group of contact-points by which they are interconnected to prevent two connections with one main switch. In the exchange described, for one thousand subscribers, the main switches are divided into ten groups of one hundred each, and to each group there is allotted a group of ten auxiliary switches. Each auxiliary switch may by proper connexions be reached from any main switch, but is normally connected only to those of the group to which it is allotted. In Fig. 4 (in which the unit is three instead of ten), four main switches out of twenty-seven are shown, together with one auxiliary switch. Should a subscriber at any station wish to call station No. 765, he proceeds as follows : He closes one of his contact-devices seven times to cause his switch to move its contact-makers P, P' under their seventh columns of contact-points, which columns are connected to the seventh group of auxiliary switches ; consequently, the parts are then in position for making a connexion to some main switch in the seventh group of main switches. He then closes his other contact-device ten times ; this causes his contactmakers P, P' to run up the column until they make connexion with an idle auxiliary switch. Six contacts are then with the first contact-device, thereby shifting the contact-makers P<2>, P<3> laterally under the sixth column ; then five more contacts with the second device raise these contact-makers into connexion with the sixty-fifth main switch of the seventh group. Fig. 3 shows one main station (calling) on the right making connexion with another (called) on the left. The subscriber first presses "1st" key once; this raises the carriage one step up, opening the contacts 73, 74 and thereby preventing anyone else from making connexion with him ; at the same time, it closes the contact 31, 32 and drops the catch C<2>. Upon " 2nd " key being pressed, the contact-makers are moved laterally beneath the required column. The "1st" key is then pressed ten times, thus raising the contactmakers till an idle auxiliary switch is reached, when a current flows from the battery Y through a circuit comprising the wires 34, 35, switch 36, 37, wire 38, magnet C, wire 39, contact-maker P', wire 41, arm E', contacts 43, 45, lever A', rack, contact 46, magnet D, and the wire 48. The current through the magnet C breaks the circuit of the magnet A at 24, thus stopping any further movement of the contact-makers. The current through the magnet D moves the carriage of the auxiliary switch up one step, breaking its connexion with the contact 46 and thus preventing another main switch from connecting up to it and removing it from the ' idle' class. A lateral and vertical movement is then given to the auxiliary switch till the required connexion is made. If while conversation is in progress another auxiliary switch, shown in the righthand upper corner of Fig. 3, attempts to connect to the same main switch, a circuit is completed through the battery Z, wires 85, 86, magnet E, wire 87, contacts 88, 89, contact-maker P<4>, wire 84, contact P<4> of the first switch, wire 90, and the contact 91. This leaves the connexions 43, 79, which form part of the talking circuit broken as shown.