Patent GB-279975-A (GB)
Title: Improvements relating to electric signalling, applicable especially to automatic telephone systems
IPC: H04Q3/42
Filed: 1926-08-30
Abstract: 279,975. Siemens Bros. & Co., Ltd., and Humphries, H. E. Aug. 30, 1926. Apparatus for signalling any of a number of possible indications.-An arrangement for transmitting signals over a control wire L, Fig. 1, in code, for use, for example, in transferring the setting of a semi-automatic telephone operator's keyboard to a registering mechanism, comprises at the sending end keys A, B for connecting to the lead L either battery or earth, and at the receiving end two relays X, Y which are connected in series with one another and with the source of current, the lead L being connected to the junction point of the relays and the circuit of each containing a break contact of the other. With key A depressed, relay X is operated, relay Y disconnected and lamp 2 lit, whilst with key B depressed relay Y is operated and lamp 3 is lit. With neither key operated both relays energize and de-energize intermittently, the operation being only sufficient to open contacts x1, y1 so that lamp 1 is lit. The number of different signals may be extended from three to five by the provision of marginal relays XA, YA, Fig. 3, in parallel respectively with relays X, Y, additional sending keys being provided which connect up earth and battery through a high resistance. By combination with a second control wire L2 having keys E, F and relays J, JA, the latter marginal, ten lamps 1 - - 0 may be controlled. For example, with keys C, F, thrown, relays Y, YA, J will be operated and lamp 4 lit. A make contact of relay J may also be employed to close the series circuit of relays X, Y. In another arrangement, both the marginal relays are connected in series in the wire L, discrimination being effected by locking windings which oppose or support the main windings according to the direction of current in the control wire. The relays X, Y are also provided with locking windings and are arranged to close one another's circuits over front contacts as well as over back contact. Alternatively, polarized or shunt field marginal relays may be employed. An additional control may be obtained by a potentiometer connection at the sending and which permits both relays X and Y to energize and remain energized. Fig. 4 shows an arrangement in which the series circuit of the relays X, Y is controlled by a relay V to prevent continuous buzzing. With key K in its first position as shown ( a open), lamp 1 is lit. With the kev in its second position (a and b closed) battery is connected to the wire L to energize relays J, Y, V and lamp 2 is lit. In order to light lamp 3, the key K after passing through its second position to energize relay V is moved to its third position (a closed and b .open) and earth is connected to the control wire to energize relay X. Figs. 8a, 8b show arrangements for signalling the position of a two-coordinate telephone call-finder switch to a central position. Extra vertical and rotary wipers P, R co-operate with extra terminals connected in pairs to battery and earth through low or high resistance as shown. In order to discriminate between the four lines having the same connection, e.g. 2 - 2, 2 - 7, 7 - 2, 7 - 7, further wipers V. Q and a further bank are provided, the four connections over wiper Q being respectively low-resistance battery, high-resistance battery, direct earth, and high resistance earth. The receiving arrangements at the central position are any of those described above. Specifications 265,732, [Class 40 (iv), Telephones &c.], is referred to.