334,205. Siemens Bros. & Co., Ltd., and Humphries, H. E. April 29, 1929. Code signal transmitters.- A self-interrupting relay device, Fig. 2, which beats with a definite period, say half a second, is used in conjunction with a relay chain A - - G, Fig. 5, to measure the duration of the marks and spaces of a selective signal, a second relay-chain H - - L being operated to close an alarm circuit if the signal is correct. A correct signal consists of three marks, each of which should be within the limits 3¢ to 4¢ seconds, separated by spaces which should not exceed 1¢ seconds each. The same apparatus serves to transmit the signal when a key AK is thrown, or automatically in case of fire &c. The timing interrupter consists of a relay Z, Fig. 2, in parallel with a condenser QA and both in series with a choke or resistance W. The interruption of Z may be effected by a relay Y under control of Z. The beating-period may be adjusted by a variable resistance YA. A normally energized relay S, Fig. 5, in the anode circuit of the last valve of a wireless receiving set is de-energized during each mark, and the operations when a correct signal is received are as follows:- First mark; measurement by relay-chain A - - G. At the commencement of the mark, SA, X, Y are energized, a charging-circuit is closed for Z, and QA is connected in shunt to Z. After a moment Z operates and de-energizes Y which opens the circuit of Z, and after another moment Z falls back and re-energizes Y, and so Y and Z continue to beat at a cyclical period of ¢ second as long as the mark persists. The first operation of Y energizes A (i); the first relapse of Y energizes B (i) in series with A (i); the second operation of Y unlocks A by closing a differential winding A (ii), B remaining locked over B (ii); the second relapse of Y unlocks B. Thus the combination A, B beats at double the period of Y; and similarly B controls the combination C, D which beats at double the period of A, B; and D controls E, F which beats at double the period of C, D. By this arrangement G is energized after 7 periods of Y (3¢ seconds after the commencement of the mark), while. C becomes re-energized 2 periods later (4¢ seconds). Relay G energizes M and H which lock. First space. At the end of the mark, SA, X, Y fall back, X being momentarily energized over its differential winding (ii) which is then shortcircuited over its own back contact. A quick discharge circuit is closed for QA, all relays of the group A - - G are unlocked, and the relapse of G permits J to energize in series with H (i). The relapse of the A - - G relays removes the self-shorting circuit from X (ii), which re-energizes and starts Y and Z beating again to measure the space. The space is assumed to be correct, i.e. less than 1¢ seconds, so that SA pulls up again before E is energized. Relay M is unlocked and Y. Z are put out of action by X, which is once more, by reason of its differential nature, momentarily de-energized until A, B, C &c., are restored, and then energizes again to start Y and Z beating. Second and third marks. These are timed like the first, G operating 3¢ seconds after the commencement of each mark and being released by X at the end of the mark. The second operation of G de-energizes H by closing its differential winding (ii) and K is de-energized and locks; the second relapse of G unlocks J; the third operation of G again energizes J. and L is energized to close an alarm circuit AB and to start a morse recorder SM, MM. The alarm can be stopped by pressing key RK to energize R, which. unlocks all energized relays. Incorrect signals. (1) A mark of more than 4¢ seconds energizes C as well as G; R is energized and releases the recorder H, J, K; at the end of 7¢ seconds and every subsequent 4 seconds a stage occurs in the cyclical operation of A - - - F when F but. not E is energized, this lasting for “ second and closing a buzzer circuit BZ; on the mark ceasing all relays are released, R last because of its copper sleeve. (2) If a space lasts more than 1¢ seconds E becomes energized, and since during a space M and either H or K are energized but SA is not, a circuit is closed for R which de-energizes X; these two relays release all other relays, and finally R itself is released. (3) A mark of less than 3¢ seconds does not operate G, M and is not recorded, and when the mark ceases all relays are released; in the case of a short second or third mark R is energized to effect the release, so that the recorder H, J, K may be restored. Transmitting code signals. When a key AK is thrown, U is energized in series with SA, X is energized and Y, Z started beating. After 4 seconds a stage is reached when G, A are both energized and U is shorted. After 4¢ seconds R is operated by G and C and de-energizes SA, which releases X to restore A - - G, and R itself is then released and re-operates SA, U and the cycle recommences. The relay U controls a wireless transmitter TM. If AK has been thrown downward the sending of 4-second marks with ¢ second spaces continues so long as the key is thrown, since the recorder H, J. K is released by R after each mark, but if AK has been thrown upward it provides an alternative holding circuit for the recorder, and at the end of the third mark L is energized and opens the circuit of SA, U to stop transmission. Signalling failure of valves. The windings of shunt-field relays P, N are connected in the filament circuits of the receiving set to energize relay L and alarm AB if any filament fails. Modifications. In a modified circuit (Fig. 7, not shown) relay S controls SA by short-circuiting it, whereby SA is made slow-to-release, so that the timing-device is less likely to be started by morse signals. The timing device A - - F is rather more complicated and tolerates marks of 3¢ to 5 seconds. Spaces are timed by a separate device comprising four slow-release relays, which are all energized at the commencement of a space and short-circuit one another in turn, the fourth falling back after 1¢ seconds. In a further modification (Fig. 9, not shown) false starting by morse signals is prevented by arranging that relay Z (which is slow to pull up because of the choke and condenser) must operate before Y can be energized. Specification 221,316 is referred to in the first Provisional Specification.