374,831. Electric signalling and remote control systems. SIEMENS & HALSKE AKT.-GES., Siemensstadt, Berlin. Dec. 12, 1930, No. 37530. Convention date, Dec. 24, 1929. Void [Published under Sect. 91 of the Acts.]. [Class 40 (i).] In a remote control system, the remote elements are selected by impulse combinations comprising positive and negative pulses or pulses of different frequencies, and are operated by the transmission of a further impulse train which is not transmitted until the position of the selected unit has been signalled back. The impulses are received by a relay chain, which is used to receive both the selecting and the operating pulse trains and to act as a distributor when the positions of the remote units are signalled back. If an adjustable member changes its position automatically an alarm signal is returned to the main station which mav initiate the transmission of a control to release a signal-back train from the substation. The system is such that no selection is made if more than the required number of pulses is received. The impulse trains may be recorded. As described impulses are transmitted by pulses of two different frequencies but any number of frequencies can be used and the specification states that the system can be adapted for the transmission of meter readings. Selection of remote unit. To select a unit a train of 6 pulses is required, the pulses being received by filters A, B and operate relays T1 or T2. The first pulse is repeated to relay Ha and if the pulse is of such frequency that T1 responds, the left hand winding of Ha is energized which allows E1 to pull up and lock. Relay Va pulls up on the first pulse and holds up throughout the train. Fourteen relays E are provided which are arranged in pairs El, E2 ; E3, E4, &c., one of each pair only operating on each pulse. E1 extends the impulsing circuit to relay Hb and breaks the initial energizing circuit of Ha so that, when T1 falls away at the end of the pulse, Ha releases. Assuming T2 responds to the next impulse then the right hand winding of Hb is energized and E4 of the second relay pair pulls up and locks, extending the impulsing circuit to the next relay. Relay Hf responds to the last pulse and, assuming T2 had passed forward the pulse, E12 of the sixth relay pair would have pulled up. A series circuit is thus completed through the operated e contacts for relay K, which completes the circuit for the required remote selecting relay Kx1 .. 6. If more than 6 impulses are received either E13 (not shown) or E14 is operated by the extra pulse and the circuit for K is interrupted. Signal-back of apparatus positions. When the selected Kx relay has operated a circuit is completed for M (Fig. 2) which completes circuits for the relays E1 .. E12. These relays lock and complete a series circuit for relay N which opens the circuit of E1. The circuits of the relays E2 .. E12 each include a contact of the E relay with the preceding number so that the release of E1 allows the twelve relavs to fall in turn. The contacts X1 .. X6 are connected with the adjustable units and connect potential to either odd or even wires of the lines 1 .. 12 which are connected in turn, as the relays E1 .. 12 release, to the relays T3 and T4. When energized, relays T3 and T4 connect different frequencies over the signalling circuit, and an impulse train is thus transmitted which indicates the position of the remote units. Operation of remote unit. Having received the check back signal, the main station transmits the control series, which comprises 6 pulses of the same frequency, so that either relays E1, E3 .. E11 or relays E2, E4 .. E12 are energized completing, when K energizes a circuit for either Ke or Ka respectively. As Va has not yet fallen the selected Kx relay is still up and this prepared a circuit for both the " in " and " out " coils Q1e, Qla of the selected apparatus unit. The circuit to energize the required one of these coils is completed bv Ke or Ka. Automatic movement of adjustable unit. Should an adjustable unit change its position automatically the circuit for relay S (Fig. 3) is completed and this relay by means of apparatus not shown initiates the transmission of an impulse train to the main station. This train may initiate the transmission from the main station of a control which releases the signal back train from the sub-station. Recording of impulse trains. The Specification states that the impulse trains may be registered by type printers or perforated strips.