Patent GB-304850-A (GB)
Title: Improvements in synchronous telegraph systems
IPC: H04L5/18
Filed: 1927-10-31
Abstract: 304,850. Beatty, W. E., (Bell Telephone Laboratories, Inc.). Oct. 31, 1927. Type-printing telegrahs.-Retates to type-printing telegraphs similar to those described in Specification 297,696 and comprises means whereby synchronism can be maintained over a cable between transmitters, repeaters, and receivers which run at the same speed, corrections being applied either backward or forward as required. Lay-out of stations. The system comprises an inland terminal station connected by land-line with a shore retransmitting station (Fig. 1, not shown), a mid-cable retransmitting station. Fig. 2, and a further terminal station, Fig. 3, the arrangement being generally similar to that described in Specification 297,696. except that the motors driving the distributers are run at equal speeds, and that the mid-cable repeating station, Fig. 2, is included. The direction of working is automatically reversed from time to time by the action of cams such as 210, 212, 330 controlling transfer relays such as 209, 211. 331. When traffic is passing from left to right, as shown, signals from the inland terminal station and shore repeating station (Fig. 1, not shown) pass via the cable 111. Fig. 2, through the amplifier 200, line relay 201, receiving distributer 202, storing relays 203, sending distributor 204 and cable 205 to the amplifier 321, Fig. 3. When, however, the direction of working has been reversed by the action of the cams 210, 212, 330, which cause the transfer relays 209, 211, 331 to throw over, signals pass from the impulse-transmitter 328 through the sending distributer 329, cable 205, amplifier 213, line relay 214, receiving distributer 215, storing relays 216, and sending distributer 217 to the cable 111. Synchronism is controlled from the sending end: thus when traffic is from left to right the incoming signals from the cable 111 operate the correction relay 206 of the mid-cable relay station, and hence the correcting apparatus 208, through the correcting rings 207, while when traffic is from right to left the incoming signals from cable 205 operate the correction relay 218, and hence the correcting apparatus 220, through the correcting rings 219. Synchronous movements.-Synchronism is controlled by the signals from the sending end in both directions of working and the distributer motors run at equal speeds. The correcting apparatus is similar at all stations, and that at a terminal station when receiving is shown in Fig. 3. Incoming signals from the cable 205 and amplifier 321 operate the correcting relay 325: at every change of polarity the armature 325a is rocked and the positive of battery 347 is disconnected from one and connected to the other of the condensers 348, 354 (which are respectively shunted by high resistances 349, 355) leading to the upper ring and the brush 332 of the correction commutators 327. When synchronism is perfect the brush 332 lies at this moment on the insulation between the contacts A, R, of which there are two to each signal impulse. If, however, the brush is lagging, it lies on a segment A and an impulse passes through the conductors 351, 352, and left hand winding of the three-position relay 333, the condensers 348, 354 being so dimensioned that this impulse is sufficient to operate the relay. The relay 333 acts to energize magnet 341, moving the shaft 343 one step and thus, through the differential gear 334, advancing the commutator shaft 336 with respect to the motor shaft 335. At the same time the magnet 333 closes a holding circuit for itself through the resistance 358, but it is short-circuited at 341a as soon as the relay 341 operates; thus the relay 333 cannot be operated a second time till the relay 341 has been de-energized. This arrangement constitutes " positive locking means " for preventing premature actuation of the magnet 341. Similarly, if the brush 332 be too advanced it lies on a contact R when the signals change polarity, and the magnet 342 is in that case operated through the right-hand winding of relay 333 and acts to retard the commutator shaft 336.