Patent GB-332572-A (GB)
Title: Improvements in the control of wireless apparatus
IPC: H03J5/24
Filed: 1929-04-20
Abstract: 332,572. Pearson, L. H., and Randall, W. J. April. 20, 1929. Distant control systems.-Wireless receiving or transmitting sets and valve amplifiers are controlled and tuned by electrical impulses sent from one or more control points preferably by dial instruments as used in automatic telephony. Loudspeakers at the control points may utilize the impulsing channel as extension leads from the wireless set. The set is preferably tuned to particular stations by switch selection from a bank of condensers &c., or the impulses may be used to step round the shaft of a variable condenser or variometer. As shown in Fig. 1, the set comprises a high-frequency amplifier VI, detector V2, and output valve V3, and the tuning condensers of the first and second stages are selected by wiper switches W5, W3, and the reaction condenser by switch W2. A switch W4 lights up the valves by connecting the negative lead LT2 to the earthed side of the filaments through the screen P; and the switch W1 selects long or short wave coils by energizing relays R1, R2. All the switch arms W1 - - W5 are operated simultaneously by a stepping-magnet SM energized by the received impulses. The wiper W1 also serves to operate indicator lamps IL1. The last valve V3 may have a choke-capacity or transformer output connection to the leads L1, L2 at the far end of which the loud speaker LS and the dial mechanism DP are situated. Direct current for the control impulses is supplied by a battery B1, B2 and is blocked from the loud-speaker transformer T by a condenser CL. Volume of sound in the loudspeaker is regulated by a resistance VC. As soon as the dial DP is moved from normal position, contacts SC are closed to short the loud-speaker, and on the return movement of the dial the requisite number of impulses is sent by opening a switch IC. The initial closure at SC energizes a relay QR which by closing its contact qr energizes a slow-release relay SR. Contact sr2 of this relay energizes the stepping-magnet. At each impulse caused by opening of the dial contacts IC1, relay QR releases and de-energizes the step magnet SM, giving one tooth advance to a ratchet wheel on the wiper shaft. The slow-release SR remains energized until the impulse sequence finishes, when the impulsing relays return to inoperative position, and the circuit L1, L2 is rendered available for voice currents by the separation of contacts SC1. Condenser SSC and resistance. SSR prevent sparking at relay contacts. When the wireless set is to be put out of operation, the maximum number of impulses is dialled, and the wiper W1 reaches the bank of connected contacts 14. After the last impulse is received over the line and relav SR is de-energized, its contact SR1 completes a circuit for the step magnet SM through an automatic interrupter SS. This generates a series of local impulses which further advance the wipers W1 until they break circuit at their rest positions. The dialling transmitter is shown in Fig. 2, the dial plate being secured to a shaft 4 carrying the notched disc 5. A mask plate 6 has frictional connection to the disc 5 and co-operates with a stop 8. During the setting movement of the dial (anticlockwise in Fig. 2) the mask 6 moves with the disc 5 until it is arrested by a stop 6<a> engaging the part 9 of the impulse contact IC1. Further setting movement exposes notches of the disc 5 from beneath the mask 6. During the return movement each of these exposed notches allows contact IC1 to open. The return movement is regulated by a governor 11. The contacts SC1, SC2 are normally open, but are closed to short the loud-speaker as long as the dial is in operation. The wiper operating-mechanism is shown in Fig. 3 comprising a shaft 15 on which the wiper arms W1 - - W5 are secured, each co-operating with its semicircular bank of contacts 19. The shaft is rotated by a ratchet wheel 21 and a horizontally-reciprocating pawl 22 pivotally supported on the lever 25. This lever carries the armature 27 of the step magnet SM and is pivoted at 26. The pawl 22 slides to the right to engage a new tooth as the magnet SM is energized, and is driven to the left by a. spring to advance the ratchet wheel 21 when the magnet SM is de-energized. The automatic interrupter SS for use in homing the wipers comprises contacts 29, 30 normally in engagement but separated by an arm 31 when the magnet SM is energized. In the modification shown in Fig. 5, a line-switch LSW takes the place of the offnormal contact SC1 of Fig. 1. When the hand switch LSW is closed, relay QR pulls up and energizes a slow-release relay SR to prepare the circuit of the step magnet SM. The dialled impulses step the magnet at each release of QR and as the wipers move away from normal position, they close contact RM. To close down the set, switch LSW is opened, relays QR, SR release, and the magnet RM is energized and allows all the wipers to be returned by a spring to their normal position. The loud-speaker may be directly in the line L1, L2 or transformercoupled thereto, and may be shorted during impulsing. Another arrangement shown in Fig. 6 employs three line-wires L1 - - L3, the line L3 being connected at SC3, whenever the dial is in position, and the line L2 at contact SC2 when the dial is off normal. Dialling impulses are thus caused to operate the stepping-magnet SM to a desired position. Homing of the wipers is effected by dialling sufficient impulses to carry the wiper W1 on to the connected contacts 14, an automatic interrupter SS providing the further impulses necessary to complete the half-revolution of the wipers. Condensers RC and resistance RS reduce sparking at the contacts. In a further modification, a line switch is provided similar to the switch LSW in Fig. 5, but the wipers rotate only in the forward direction, and are brought to normal position by stepping them forwards by impulses provided by an automatic interrupter (Fig. 7, not shown). In the arrangements of Figs. 5 and 7 the valve filaments may be lit by contacts controlled by the relay SR instead of employing a separate wiper W4 as in Fig. 1. Moreover the distributing lines L1, L2 may be connected to the set by a slow-to-make relay energized by contacts on the relay SR. Where the set is to be controlled from a number of points, series or parallel connections may be employed. With the series arrangement, bridges provided to maintain a complete circuit when a loud-speaker is removed may also serve to short the dial apparatus. The dial may be in one unit with the loud-speaker, and the unit may be plugged in at the control point. When the set is tuned by variable condensers, as distinct from selected condensers, tens and units may be dialled in succession, the tens impulses stepping the condenser shaft forward in large steps, and the units in smaller steps. The dialled impulses may also function by selecting a particular stop and displacing it so as to arrest the movement of a condenser or variometer shaft at a selected setting. Such stops may operate mechanically, or may comprise electric contacts which when operated de-energize the step magnet.