Patent GB-244814-A (GB)
Title: Synchronising systems
IPC: H04L7/00
Filed: 1924-09-17
Abstract: 244,814. Western Electric Co., Ltd., (Western Electric Co., Inc.). Sept. 17, 1924. Synchronous movements. - A synchronizing system, particularly intended for use in high speed multiplex telegraph apparatus, involves the use of a thermionic amplifier associated with a distributor receiving impulses transmitted over a line, an electromagnetic device for controlling the means for driving the distributor being included in the output circuit of the amplifier. The invention is mainly characterized in that the action of the said electromagnetic device in effecting a speed correction is determined solely by potential variations in the input circuit of the amplifier, brought about by means of a relay responsive to the line impulses. The system shown in Fig. 1 comprises a controlling station A and a controlled station B, each of which includes a distributor driven by a phonic wheel 10 or 10<1> under the control of electrically-maintained forks 12, 12<1> respectively. The fork 12 is kept at a constant rate of vibration by the following means. Adjacent to one leg of the fork is a polarized electromagnet 15, which is connected to the primary of a transformer 16, the secondary being. connected in the input circuit of an amplifier 17. The output side of the amplifiler is connected to an electromagnet 19 adjacent to the other leg of the fork. A variable condenser 20, a variable inductance 21, and an adjustable resistance 22 are arranged as shown to enable the circuit on the input side of the amplifier to be tuned. As the fork vibrates it generates an alternating current in the coil 15, and thus, when the tuning devices are suitably adjusted, impulses are supplied to the magnet 19 whereby the fork is maintained at a constant frequency and amplitude of vibration. A similar arrangement is provided at the station B for controlling the fork 12<1>, but, in addition, means are provided for automatically interfering with the tuning of the oscillating circuit, such means consisting of a condenser 42 which is connected across the condenser 20<1> or disconnected therefrom by the operation of a relay 36 in the manner described below. At each station A, B the phonic wheel drives the rotary brush arm 23 or 23<1> of a distributor. In order that either station may, when desired, be operated as the controlled station, the distributors are preferably alike, and include correcting-segments 29, 29<1> as well as receiving and transmitting segments. The latter are arranged to transmit Baudot code signal impulses through the respective contact rings 32 or 32<1>, each of which is connected to a line relay 35 or 35<1>. Artificial lines AL are preferably pro. vided for duplex working. At the controlled station B, the correcting segments are divided into two sets, alternate segments being connected together and respectively to the upper and lower terminals of the relay 36. The two terminals of the line relay 35<1> are respectively connected through a resistance 39 and condenser 40 in parallel and a resistance 37 and condenser 38 in parallel to the contact ring 30<1> associated with the correcting segments. The arrangement is such that with each change in sign of the signal received at the relay 35<1> (assuming that station A is transmitting) a charging impulse is sent through one of the condensers 40 or 38, the impulse passing through either the upper or the lower or through both windings of the relay 36, according to the position of the brush 25' in relation to the segments 29<1> at that instant, If the distributor at station B is lagging when a signal impulse is received, the brush 25<1> connects a " slow " segment S to the ring 30<1>, and the armature of the relay 36 is moved to or remains in the position shown, connecting the condenser 42 across the condenser 20<1>. The control circuit of the fork 12<1> is thus detuned: consequently the amplitude of the vibrations diminishes and the frequency increases. This action is repeated until the speed of the controlled motor is restored to the normal, and the converse action occurs if the speed becomes too great. Various modifications in the devices for tuning the circuit on the input side of the amplifier are described. For example, an auto-transformer may be used in place of the transformer 16. Fig. 6 shows another arrangement for use at a controlled station, whereby the frequency of the fork F is controlled by varying the resistance in the circuit of its operating electromagnet. This magnet 132 is connected to a battery 130 through a resistance 131, which is normally short-circuited by an armature 128. This is influenced by two coils, the coil 122 being in the plate circuit of an amplifier 117, and the other coil 124 being supplied from a battery having a variable resistance 127 in circuit. Adjustments are made so that the action of the coil 122 normally overcomes the action of the coil 124, the armature being held against the contact 129. An impulse relay 111 is connected through a condenser 108 to a line relay 105, so that each time a signal impulse is received the relay 111 operates, and connects the negative pole of a battery 114 to a ring 112 of the distributor driven under the control of the fork. Should the fork be lagging, the brush 139 will connect the ring 112 to a segment 116 at the instant when the relay 111 acts, whereupon negative potential is applied to the grid of the amplifier, the current in the coil 122 weakens, and the armature 128 moves to the position shown. The current in the magnet 132 is thus reduced by the resistance 131, and the rate of vibration of the fork increases. In a further modification, Fig. 7, the frequency of the fork is controlled by variation of a magnetic field within which the tines of the fork vibrate. This field is provided by an electromagnet 141, the poles of which are aligned with the tines. The magnet has two windings 142, 140, included respectively in circuit with a battery 143 and in the plate circuit of a valve 121. A resistance 145 is first adjusted so that the combined magnetic effect of the coils 140. 142 under normal conditions keeps the fork vibrating at the required frequency. The input circuit of the valve is varied in the same way as in the arrangement shown in Fig. 6, so that connections are automatically produced by variations of current in the coil 140.