Patent GB-190426282-A (GB)
Title: Improvements in Switch Installations for Telephone Exchanges and in Switches therefor.
Filed: 1904-12-02
Granted: 1905-03-30
Abstract: 26,282. Siemens Bros. & Co., [Siemens & Halske Akt.-Ges.]. Dec. 2. Telephone systems.-Relates to switch installations for telsphone exchanges, in which specially constructed rotary switches are employed for connecting the subscribers, one such switch being associated with each subscriber's line-wire. Fig.1 shows one of the switches secured in place on the switchboard t. The subscribers' line-wires are connected either through flexible wires or through slip rings with the contact-springs a, which are adapted to make contact with blocks d arranged in a circle and connected to wires f. In order to shift from one diametral pair of contact-blocks d to another, it is necessary first to depress the switch handle i against the pressure of a spring m, and thereby to release a transverse pin g carried by the shaft b from its engagement with the corresponding pair of notches in the ring h. The springs a are thus prevented from making contact with those blocks passed over in moving to the new position. A pointer o moving over a scale of numbers indicates the contacts closed by the switch at any time. The shaft b passes through a stuffing- box to prevent moisture &c. from reaching the back of the switchboard. In order to connect the subscriber's line with the exchange operator's telephone, provision is made either for depressing the shaft b by means of a knob u to a greater extent than is done by the handle i, and thereby making contact between a and p, or, by increasing the width of the notch in which the pin g normally rests, to allow of a slight rotary movement of the shaft without depression, so as to make contact between the springs a and a special pair of contact-blocks, which are indicated at v in Fig. 4. Fig. 4 shows diagrammatically an exchange for four subscribers. In the normal position of the contact-springs a, the subscribers' lines are con. nected to the annunciators z. In the position shown, subscriber III has made a call, and his switch has been operated so as to put him in communication with subscriber I. If the contactsprings a of switch I are moved into contact with the blocks v, as already described, the operator's telephone set A is bridged across the talking- circuit without interrupting it. The call indicator of the subscriber called up serves to give the clearing-signal. In the arrangement shown in Fig. 4, each switch must have as many pairs of contact-blocks as there are subscribers connected to the exchange. In a modification, independent connecting-leads are used, of which there are as many pairs as the maximum number of simultaneous conversations allowable. In this case both switches are operated to connect the two subscribers across one of the disengaged pairs of leads. A common battery may bridge the leads, which may be provided with galvanometers &c. to indicate those engaged. Separate clearing-indicators bridge the pairs of leads. An extra rotary switch enables the operator's set to be bridged across any pair of leads. Each switch may be provided with an extra arm for closing independent indicator circuits for the purpose of showing which leads are in use at any time. The system is described as applied to a special case in which three suburban post offices are connected together, and are connected also to two exchanges and a private wire, but the latter can be put into communication with the post offices only.