GB565314A - Improvements in or relating to electric signalling systems - Google Patents

Abstract

565,314. Automatic exchange systems. WESTERN ELECTRIC CO., Inc. Aug. 20, 1943, No. 13593. Convention date, Oct. 9, 1942. [Class 40 (iv)] [Also in Group XL] Connections are extended over constantly rotating cathode beam switches, e.g. switches similar to those described in Specification 539,315, [Group XL], in tandem. In the absence of any control, these switches 100, 102, 103 rotate in synchronism. When a line calls, however, an up-and-around mechanical switch 109 hunts for the calling line and connects it to a register 110 which takes the wanted number. The switch and register control two phaseshifting networks in the circuit controlling the switch 102 in accordance with the calling and called numbers and so alter .the phase of 102, which continues to rotate isochronously, that its beam makes contact with the wanted line at the instant that switch 100 makes contact with the calling line. To enable the same switch 100 to be used for a number of simultaneous conversations through different switches 102, 103, it is arranged that the beam in the latter switches is suppressed except at the moment that the beam in 100 is making contact with the particular calling line concerned. The beams make effective contact between individual targets and a common collector grid for two-way conversation by reason of secondary emission. Construction of cathode-ray tube. As shown in Fig. 8, the collector grid 801 is provided with ears such as 809, 810 to confine the secondary emission from a particular target and prevent interference between adjacent circuits. The beam can be suppressed by a control grid 812. Detailed circuit arrangements. When a subscriber calls, a two-motion call finder hunts in known manner for his line, at the same time moving condenser plates 407, 409 in relation to four quadrants connected to a. bridge circuit to vary the phase of the current picked up by these plates. In order to ensure that a rotary step will cause only one-tenth the phase shift of a vertical step, the supply frequency is multiplied by 10 at 433 before being fed to the bridge and the current picked up by the adjustable plate 409 is"divided by 10 at 434. The same effect can be produced without frequency multiplication by causing the units movement to move the plate 409 at each step only one-tenth the distance moved by plate 407. The final result is that the current in circuit 432 is shifted in phase with respect to the supply current by 36 degrees for each vertical step and by 3.6 degrees for each rotary step. The current from 432 then undergoes a similar phase shift in the opposite direction in accordance with the tens and units digits dialled, the resulting current in circuit 509 correspondingly controlling the phase of the beam 316 in switch 300. The beam is normally suppressed by a voltage applied to the control grid 310, but an impulse sent over circuit 446, whenever the beam in the primary switch 206 encounters the calling line and speech is on the line, renders it effective momentarily. Further conversation can take place simultaneously through the switch 206 and other secondary switches such as 301.