Patent GB-190314204-A (GB)
Title: Improvements in or relating to Telephone Systems with Central Battery
Inventor: PILTZ GOTTLIEB MAGNUS TEODOR
Filed: 1903-06-25
Granted: 1903-08-06
Abstract: 14,204. Piltz, G. M. T. June 25. Telephone s y stems. - In telephone systems with a central battery, when at the exchange a connecting-plug is inserted in a jack appertaining to a subscriber's line, two inductive resistances are interposed in the circuit supplying the transmitter with current from the central battery. One of these resistances is interposed between one pole of the battery and one conductor of the cord, which conductor is connected by means of the plug with one branch of the subscriber's line, while the other resistance is directly interposed between the other branch of the subscriber's line and the other pole of the battery. Both the inductive resistances are constructed to form relays, namely, one, interposed in the line, to form a cut-off relay for the calling- signal device, and the other, interposed in the cord, to form a controlling-relay for the clearing-out signal. Fig. 2 illustrates one form of the arrangement. When the subscriber, by unhooking his transmitter, establishes connection between the line branches 1, 2, the following circuit is closed:- Battery 35, contact 40, line branch 2, transmitter 3, receiver 4, line branch 1, winding of relay 36, contact 39, and earth. The energized relay 36 closes another circuit at 38, through which the calling-signal lamp 37 is lighted up. The operator at the exchange now inserts the plug in the subscriber's jack, and a circuit from the central battery 23 is established in the following way :- Central battery 23, inductive resistance 6, cord conductor 28, contact 10, line spring 8, line branch 2, transmitter 3, receiver 4, line branch 1, line spring 7, plug conductor 9, sleeve 34, relay 5, and earth. The inductive resistances 6, 5 thus interposed on each side of the battery prevent the speech waves leaving the main line. The relay 5 attracts two armatures and breaks two circuits at 39, 40, upon which the lighting of the calling-up lamp 37 depends. The relay 6 breaks at 26 the circuit of the relays 25, 5, and the operator inserts the plug 19, 20 in the spring jack of the number desired, thereby establishing analogous circuits in the right-hand part of the Figure. When the conversation is finished, the subscriber replaces his transmitter on the hook and breaks the circuit between 1, 2. This, through the relay 25, closes the circuit of the clearing-out lamp 30, which will continue to glow till the plug is removed from the jack. Condensers 21, 22 are inserted in the cord conductors 28, 29. In the arrangement described, there are three conductors 7, 8, 34 in the jack ; a modification is described in which there are only two conductors. In this arrangement, the inductive resistance, connected with one branch of the subscriber's line comprises two relays, one of which is energized when the subscriber calls the exchange, and the other when the plug is inserted in the answering-jack of the subscriber's line, by which operation the latter connects the two relays in parallel so that they act together as an inductive resistance. Another modification is adapted for calling one or the other group of switchboards in a divided multiple-switchboard system of two sections. Each line branch is connected with one of two relays, through one or the other of which a circuit is closed when the corresponding line branch is grounded at the subscriber's station, so that the said relay attracts its armature, thereby closing a second circuit through the winding of the same relay in such manner that the said winding is supplied with current even after the corresponding line branch has been disconnected from the earth at the subscriber's station.