Patent GB-130408-A (GB)
Title: Improvements in and relating to Electric Relays.
Inventor: TURNER LAURENCE BEDDOME
IPC: H03D11/02
Filed: 1918-02-16
Abstract: 130,408. Turner, L. B. Feb. 16, 191b Thermionic relays. -The grid potential of a lamp relay is adjusted to a value just below the critical value at which the lamp begins to generate oscillations, in order that a small increase of the grid potential produced by a signal or other current may cause the lamp to operate, and the plate circuit of the lamp contains a relay which controls an indicator circuit, and the lamp is quenched by the action of this relay, by a separate switch, or by modifying the lamp circuits. A lamp amplifier may be placed between the signalling-circuit and the lamp relay; and when the relay is employed on cable circuits, the signal currents are broken up by an interrupter. The circuits of the relay are modified in order that the grid potential may be varied in one direction only, and this function is performed by the amplifier when used in connexion with the relay. In doublecurrent working, two relays are employed; and the effects of earth currents are eliminated by applying to the grid a potential equal and opposite to that produced by the earth currents. In the arrangement shown in Fig. 1, the grid circuit of the lamp relav V contains an inductance Ig, the secondary winding T
 of a transformer, and a battery B<g> by means of which the potential of the grid G relative to the negative side of the filament F may be adjusted. The plate circuit of the relay contains an inductance I<a> coupled to the inductance I<g>, a relay CR, and a battery B<a>. The controlling- current is supplied to a primary winding T<p> of the transformer and is arranged to raise the potential of the grid G relative to the filament F, and the relay oscillates to energize a relay CR adapted to control an indicator circuit and to short-circuit the circuit C<a>, I<a> to quench the relay. The shunting condensers C<g>, Ca of the inductances I<g>, I<a> may be dispensed with, and the quenching may be performed by a separate switch. In a modification, a condenser is placed across the filament and grid and across the filament and plate of the relay, these condensers being connected to the ends of the inductances I<g>, I<a> remote from the grid and plate respectively. Also the potential of the grid relative to the filament may be varied by means of a potentiometer connexion across the battery Bf. In a further modification, the filament circuit contains a resistance placed between the negative end of the filament and the grid to compensate for small potential variations of the filament battery Bf. The arrangement is applied to wireless signalling by tuning the grid circuit I<g>, 4, Ts, Fig. 5, to the aerial circuit TP, 3. When applied to cable telegraphy, the currents received from the cable 5, Fig. 6, are broken up by a switch 8, 9 and passed through the primary winding TP of a transformer. A switch 8, 10 controls a shunt about the circuit I<a>, Ca to quench the relay. The switch 8, 9 is arranged so that the effective current is produced at the break and not at the make of the switch, and reversal of current in the transformer winding TP, T
 is prevented by means of shunt resistances 12, 13. In the arrangement shown in Fig. 7, a lamp amplifier V<1> is placed between the signalling-circuit and the lamp relay V, and the potential of the grid G<1> of the amplifier is raised to such a value that the current through the valve passes in one direction only, thereby avoiding the use of the shunt resistances 12, 13. The effects of earth currents are eliminated by placing a resistance r, Fig. 8, having a large temperature coefficient adjacent to a cooling-element 14 the position of which, relative to the resistance r, is varied by a galvanometer energized by portions of the signal and earth currents. The resistance r is connected in circuit with another resistance r<1> and a battery B<r>, and the arrangement is such that potential charges of the grid due to earth currents are compensated for by variations of potential across the resistance r.