Patent GB-890820-A (GB)
Title: Improvements in or relating to telecommunication systems comprising transfluxors
IPC: H04Q3/52
Filed: 1958-08-13
Abstract: 890,820. Telephone systems; controlled non- linear inductors. PHILIPS ELECTRICAL INDUSTRIES Ltd. Aug. 13, 1958 [Aug. 16, 1957], No. 26027/58. Classes 40 (4) and 40 (9). [Also in Groups XL (b) and XL (c)] In a telegraph or telephone system, a transmitter is selectively connected to a receiver by one or more transfluxors which are brought from the closed to the open state by a control device connected to the transfluxor control windings, and information is passed by way of the transfluxor controlled windings in the form of alternate positive and negative pulses having characteristic intervals. Each transfluxor comprises an apertured cylindrical core 1 of rectangular hysteresis loop material such as a ferrite having relative dimensions a and 2a between the apertures 2, 3 as shown in Fig. 1. In operation, a strong control pulse is applied to a control winding 4 so as to establish remanent magnetic fields 7 and 8, Fig. 2. Substantially no coupling now exists between the controlled windings 5 and 6 and the transfluxor is said to be in the closedstate. If, now, a control pulse of opposite polarity and lesser amplitude is applied, the direction of the inner field 7 only is reversed, Fig. 3, and the transfluxor is brought to the open state A. Close coupling is now available between the controlled windings 5 and 6, since the application of alternate positive and negative pulses to winding 5 establishes positive and negative remanent fields 14 in turn around the aperture 3 as shown in Fig. 4 (state B) and Fig. 5 (state C), thereby inducing a corresponding output in winding 6. In an application to telegraphy, a matrix of transfluxors 200-248, Fig. 6, have their controlled windings connected in columns 51-111 and rows 121-181, each when open . providing a path between a morse transmitter 50-110. and a receiver 120-180. Selection of a given path is effected by a control member 45 which applies coincident pulses to a column control wire 52- 112 and a row wire 122-182, the single transfluxor acted on by the coincident current pulses being changed from the closed to the open state A. A single transmitter-receiver, circuit is shown in Fig. 7 in which morse-coded pulses generated by a key 63 in a transmitter 60 are converted into alternate positive and negative pulses by a differentiating circuit 67, the duration or interval between a positive and the succeeding negative pulse being indicative of the code impulse. These alternating pulses are passed by an open transfluxor 222, whichalternates between states B and C, to a receiver 150 where the pulses are amplified at 153 and operate a bi-stable circuit 154. The output of the bi-stable circuit controls a morse receiver 156 by way of a valve 155. A matrix of transfluxors 1102-1806, Fig. 8, may be used to provide selective connections between subscriber's substations 1100-1800, each transfluxor having column and row control wires 1107-1807 and 31-35, and two controlled wires each comprising the two conductors of a telephone line. Initially, all the transfluxors are in the closed state. In operation, a calling subscriber causes the associated line circuit 1101-1801 to transmit a signal to a control device 21 which tests over lead 26 if the register 20 is free. If this is the case, the control device 21 applies coincident pulses over a row wire 31 and a column wire 1107-1807 to the transfluxor in the group 1102-1802 associated with the calling line. This transfluxor is brought to the open state and permits a signal indicative of the substation required to pass over wire 25 to the register. This information is transferred to the control device 21 which applies coincident pulses both to the column wires 1107-1807 pertaining to the calling and called substations and also to a pair of row wires 32, 33 or 34, 35, depending on which of two connectors 22, 23 is free. Two transfluxors are therefore brought to the open state and a speech connection is set up over these transductors and one of the connectors. The transfluxors are restored to the closed condition by pulses of opposite polarity from the control device when both parties hang up. A completed circuit between substations 1200 and 1500 is shown in Fig. 9, the circuit comprising line circuits 1201, 1501, open transfluxors 1.203, 1504 and a connector 22. Each line circuit includes a changeover switch 1224, 1524, which are brought into respective opposite positions, and a triangular voltage wave b, Fig. 10, and a train of alternating pulses c of high repetitive frequency are applied to terminals 40, 41 and terminal 42 respectively. In operation, each line circuit in turn produces a negative pulse, the duration of which from a reference pulse is determined by the instantaneous value of the speech voltage from its respective substation. This pulse is transmitted to the other line circuit where it is reconstituted as a speech voltage element, the transfluxors in the transmission path being thus subjected to alternating pulses as required by their mode of operation. The line circuit 1201 commences a pulse f when a positive pulse c at terminal 42 operates a trigger pair 1219. The pulse f is subsequently terminated by restoration of the trigger pair, this restoration being effected by the positive-going portion of a waveform e which is derived from the secondary winding 1217 of a transformer 1218 to which the triangular waveform b and speech voltage d is applied by primary windings 1216 and 1212 respectively. The pulse # is applied to a differentiating circuit 1220, rectifier 1231 and amplifier 1221 so that only the negative portion of a resultant alternating pulse g is transmitted to the other line circuit 1501. At this receiving line circuit a positive c pulse operates a trigger pair 1522 which applies an output h over a low-pass filter 1523 to the substation 1500, the output h being terminated by restoration of the trigger pair when the negative g pulse from the transmitting line circuit is received. Subsequently a trigger pair 1519 is operated by a negative pulse c at terminal 42, and a negative g pulse is transmitted in due course to the line circuit 1201 where it resets a trigger pair 1222. It is stated that the connector circuits may comprise transistors.