Patent GB-567451-A (GB)
Title: Improvements relating to electric signalling systems
IPC: H04Q3/52
Filed: 1943-08-13
Abstract: 567,451. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., and CHRISTIAN, D. A. Aug. 13, 1943, No. 13186. [Class 40 (iv)] [Also in Group XL] In an automatic exchange system in which connections are extended over cathode beams, each of the targets individual to a wanted talking circuit is divided in halves connected respectively to the ends of the centre tapped primary of a transformer such as TR2 and, in the absence of speech currents, the tip of the beam rests equally on each half of the selected target. Speech voltages are applied to subsidiary deflector plates which disturb this equality and so cause speech currents to appear on the secondary of the transformer. Analogous arrangements are used for the transmission of speech in the other direction. In the twodigit system shown, a calling line is permanently coupled by a hybrid coil to all the subsidiary defectors of a tube CRA and all the pairs of targets of a tube CRB for outgoing and incoming speech respectively and has a third tube CRC for testing the wanted line. A, B and C relays operate in known manner and the digits sent as ordinary or voice-frequency impulses are registered on tens and units switches TS, US. On the relapse of CC at the end of the units digit, a circuit is made for relays P and Q in series, the response of the latter being delayed by a slug. P applies potentials selected by the tens and units switches to the ordinary deflecting electrodes of all three cathode-ray tubes. If the line is idle the beam in the test tube initially rests wholly on the upper of a pair of targets CTP, which is multipled to all the corresponding electrodes in the tube and may be in the form of a strip extending along the row. As a result, a relay T individual to the tube energizes TT and applies a repelling potential to the upper of two subsidiary deflectors CSP1, CSP2. This electrode is multipled to all the similar electrodes in the tube. The beam is thus caused to make contact with the lower target CTP2, which is individual to the wanted line and a relay N individual to that line and common to all the selectors giving access to it pulls up and applies a holding potential to the individual subsidiary deflector CSP2 The relay N shown is actually that of the line previously assumed to be calling. Relay N is followed by a relay NN which connects ringing current to the line via a trip relay TR which completes the connection when the called party replies, both these relays being part of the equipment of the wanted line. If the wanted line is busy, the lower subsidiary deflector is energized and the beam does not make contact with the upper target. Consequently, relays T, TT remain inert and, when Q pulls up, P is shunted out and the beams are all restored to normal. When the calling party hangs up, the switches go home. The line-testing arrangement forms the subject-matter of Specification 567,674. Tube construction. In addition to the usual focusing and deflecting electrodes, the tube has pairs of targets electrodes ATP, a plate AWP with apertures for shaping the top of the beam or a system of subsidiary deflectors ASP for deflecting the beam from one to the other of the target electrodes of a selected pair. These subsidiary deflectors may be individual to a pair of targets or as shown common to a row. In another arrangement, all the upper targets are connected together, those in each row being formed by a continuous strip and all the upper deflectors are similarly connected together, the lower targets and deflectors being individual. and in another, all the deflectors are individual and all the upper targets are connected together and all the lower targets connected together. Repeater circuits. In the outgoing tube CRA, all the upper subsidiary deflectors are connected together and to one end of transformer TR1 and all the lower ones to the other end. In consequence, outgoing speech causes oscillating of the beam over the selected pair of targets to produce speech currents in the associated transformers such as TR2, these currents being amplified and fed via a hybrid coil HB2 to the called line. Incoming speech affects the potentials of subsidiary deflectors, such as BSP1, BSP2, individual to the called line, and so controls the play of the beam over the pair of targets BTP1, BTP2 (which are constituted by continuous strips) and consequent generation of speech currents in transformer TR3. These currents are amplified and fed to the calling line via a hybrid coil HB1.