Patent GB-464551-A (GB)
Title: Improvements in or relating to interconnecting circuits for telegraph repeaters
IPC: H04L25/04
Filed: 1936-07-18
Abstract: 464,551. Code telegraphy. STANDARD TELEPHONES & CABLES, Ltd. (Western Electric Co., Inc.) July 18, 1936, No. 19939. [Class 40 (iii)] In a system in which telegraph signals over one of a number of lines each terminating in a repeater are repeated simultaneously over all the other lines, for example, for broadcasting information, the repeaters are connected together by a single-wire parallel or series connection. In the system shown in Fig. 1, repeaters A, B, C, terminating two-way subscribers' loops L1, L2 and a four-wire circuit L3, respectively, are connected through singlewire " spokes " SP1, SP2, SP3, to a common " hub H. Normally all the sending relays S of the repeaters are operated to marking by their biassing right-hand windings and there is no current in the spokes or hub. When a signal over line L1, say, operates relay R1 to spacing, the positive pole of battery B is connected to the hub circuit and the left-hand windings of the other sending relays S2, S3 are operated in parallel to repeat a spacing signal over lines L2, L3. Jacks J1, J2 may be connected in the spoke circuits for testing or monitoring purposes. In the system shown in Fig. 2, a single-wire series circuit normally extends through the right-hand windings of all relays S and operates them to marking. When a signal over line L1 operates R1 to spacing, the right-hand windings of relays S2, S3 are opened and the relays are operated to spacing by current in the left-hand winding - (the line-current in the case of S2 and biassing current in the case of S3). Relay S1 is prevented from responding to the signal by the provision of a resistance 15 reducing the current in the left-hand winding and by a condenser, so that the current in this winding falls to zero before that in the right-hand winding. In the repeater C, two sending and two repeating relays are provided relay S4 operating in series with S3 to prevent operation of R3 at this time, and relay R3 being controlled by R4 and in turn controlling the series connection H. The lines L1, L2, &c, and both sides of the repeaters A, B, &c., may terminate in jacks, and the hub circuit H be associated with multipled jacks so that by means of patching cords any desired combination of lines may be connected together for simultaneous repetition. The contacts of the receiving relays R may be bridged by condensers and connected to the hub H through inductance coils to reduce sparking and the biassing of the circuit in favour of marking. In another arrangement, Fig. 5, the sending relays S1 are normally biassed to marking by resistance connections 11, 12, 13, to the two poles of battery, and are operated to spacing when the positive pole is directly connected to circuit H at another repeater. In order to indicate whether the hub and spoke circuits are faulty, alarm-controlling normally-energized sensitive relays may be connected between the armatures of relays R, Fig. 1, and the negative pole of battery, a corresponding number of parallel high resistances being connected between circuit H and the positive pole. A similar alarm relay ARl and resistance N1 are shown in Fig. 5..