Patent GB-191315828-A (GB)
Title: Improvements in or relating to Telephony.
Inventor: BROWN SIDNEY GEORGE
IPC: H03F13/00
Filed: 1913-07-09
Granted: 1914-07-09
Abstract: 15,828. Brown, S. G. July 9. Telephonic repeaters.-Relates to telephone relay systems of the kind described in Specification 9179/12, in which, when voice -currents from the transmitting station actuate the relay apparatus, the receiving station is rendered incapable of operating the relay apparatus but is connected with the magnified voice-currents produced thereby. According to the present invention, the person speaking is permanently in effective connexion with the distant station until the person at that station speaks. The device which is responsive to the voice currents and co-operates with the relay apparatus may be made less delicate than was previously necessary, and means are provided to guard it against disturbance from external influences on the line. Fig. 1 shows the parts in the positions they occupy as long as the subscriber on line A is speaking, the voice-currents from line A inducing currents in the line proper L<a>, so that the transformer winding E<1> is the source of variable currents by which the voice-current relay C is energized, and the transformer winding F' serves to transmit magnified voice-currents from the terminals C<2> of the relay C along the line L<b> to the subscriber's line B. When, however, the subscriber on line A stops and the subscriber on line B commences to speak, the vibration-switch B<5>, which may comprise a pivoted arm having a carbon contact resting on a reed serving as the armature of an electromagnet, and also provided with a carbon contact, rapidly interrupts the circuit of the battery B<3>, so reducing the current passing through the post office relay B<4>, the armature g<1> of which moves into contact with the terminal g. The circuit of a battery B' is thus completed through the lines L<b>, so energizing the coils d<1>1, d<2>1 of the double-pole change-over switch D, and moving the switch arms D', D<2> to the positions shown in dotted lines. The switcharms D', D<2> are preferably of the overbalancing type, and remain in the same position until the coils d<1>, d<2> are energized. The voice-currents in line B induce currents in the line L<b>, so that the transformer winding F<1> is now the source of variable currents by which the relay C is energized and the transformer winding E<1> transmits magnified voice-currents from the terminals C<2> of the relay C along the line La to the subscriber's line A. In a modification, the batteries A', B<1> are connected either through inductances or not to the middle of inductances connecting the lines La, Lb. The spring-controlled armatures g<1> of the electro-magnet A<4> and relay B<4>, and the lines between the electromagnets of the switch D are earthed. In another modification, the relays A<4>, B<4> are dispensed with, and one contact of each vibration switch A<5>, B<5> is connected through an inductance connecting the lines La or L<b>. The other contact of each switch A<5> or B<5> is earthed, and the batteries are inserted in the earth connexions between the electro-magnets of the switch D, so that the four electro-magnets controlling the switch arms D<1>, D<2> are normally energized and two of them are de-energized when a subscriber speaks. The vibration switches A<5>, B<5> are preferably arranged close to the subscriber's lines, and their electro-magnets may be arranged across the lines L<a>, L<b>, but are preferably connected across the arms A<6> of a bridge connexion, as shown in Fig. 1, in order to prevent disturbances in the line and currents from the relay C actuating the switches. One end of each bridge arm A<6> is connected to the line L<a>, and the other end is connected to part of the transformer winding by which the line La is coupled to the subscriber's line A. A<7> represents an artificial line which is a copy of the subscriber's line. As shown in Fig. 3, the vibration switches A<5>, B<5> may be arranged close to the transformers E, F, so that the operator at the relay station may adjust them if necessary. When voice-currents traverse the line L<a>, the switch A<5> reduces the current in the circuit of the battery A<1>, so that the magnets controlled by the switch E<5> predominate, and the switch arms D', D<2> move to the positions shown. The voice-currents then operate the relay C and the reinforced currents act on the line L<b> through the transformer F. The currents induced in the line Lb operate the vibration switch E<5>, but as the switch arms D<1>, D<2> are of the overbalancing type, this is immaterial provided the vibration switch A<5> does not become quiescent and so energize the electro - magnets which move the switch arms D<1>, D<2> to the alternative position. To guard against this, the voice-currents may be tapped by a transformer H to energize coils A<Î>, B<Î> associated with the switches A<5>, B<5>. The two coils of each switch A<5>, E<5> are preferably arranged to oppose each other, the electrical characteristics of the circuit of the coils A<Î>, B<Î> being made equal to those of the lines L<a>, L<b> by introducing an artificial line J. The switch B<5> is then quiescent and the switch A<5> is active, because its two coils are energized by currents of different magnitudes, as long as voice-currents traverse the line L<a>. In a modification the coils AX, B<Î> are dispensed with, and a third vibration switch having its coil in circuit with the transformer H is employed. The contacts of this switch are in the circuit of the battery B<1> and the coils of the switch arms D', D<2>, so that as long as voicecurrents are flowing in the line, these coils are not energized.