430,602. Selectors responsive to code signals. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, REED, M., 25, Weigall Road, Lee, both in London, and TOWNEND, F. J., 252, Eden Park Avenue, Beckenham, Kent. May 2, 1934, No. 13252. [Class 40 (iv)] [See also Group XXXVIII] Apparatus for responding to signals comprising equally spaced marks of equal length with a certain tolerance and for transmitting such signals accurately, includes three condenser-resistance timing-circuits in association with a single gas discharge tube. As described, the condensers are normally charged and cause the tube to strike after a predetermined period of discharge. Alternatively, the tube may strike after a predetermined period of charging. The three circuits are arranged during reception of a signal to check the minimum and maximum lengths of the marks and the maximum length of the spaces. For transmission, circuit changes are brought about whereby two of the timing-circuits measure the correct lengths of the marks and spaces. Reception of correct signals. When the apparatus is connected up for reception, the switch TR being in the position shown, relay S energizes in the anode circuit of the receiving valve RV, while V energizes in the filament circuit in series with a lamp FL. Failure of a valve results in the relapse of V and the extinction of FL, relay N operating to connect in the alarm AB. On receipt of the first mark, S falls back and connects up SA(i) which closes the discharge circuit for the condenser QC through the resistance R1. After 3¢ seconds, the neon tube NT strikes and relay C operates CA which locks, connects up H(i) and associates the tube NT with the timing circuit QE, R2. When the mark ceases, e.g. after 4 seconds, SA falls back and connects up G which locks and associates the tube NT with the timing circuit QF, R3 to time the space. After the condenser QF has discharged for 1¢ seconds, the tube NT strikes and relay F disconnects CA, G. Since SA has now been reoperated by the second mark, H(i) holds in series with J(i), which energizes due to the removal of a short-circuit. The first timing circuit QC, R1 is effective as before to time the second mark, and CA closes a parallel circuit through H(ii), J(ii). Relay J holds, but H falls back due to its windings being in opposition, and relay K pulls up. After the second space, CA falls back and disconnects J, so that the next operation and relapse of CA at the end of the third mark and the succeeding space bring about the re-energization of H(i), J(i). Relay N energizes, locks, disconnects SA, and connects in the alarm AB. Rejection of incorrect signals. If a mark is too short, SA falls back before the condenser QC has discharged sufficiently to operate C, CA and the circuits of H, J, K are opened. If a mark endures for 4¢ seconds, the condenser QE discharges sufficiently for the tube NT to strike and relay E operates EA which locks and disconnects CA, H, J, K. The condenser QE recharges and subsequently discharges over the resistance R4, so that the tube NT strikes at intervals of a second as long as a mark continues, operating a buzzer BZ to call attention to a jamming signal. If a space is long, SA is still back when CA is disconnected by F, consequently the circuits of H, J, K, are opened. Transmission of signals. The switch TR is thrown over to operate relay P which substitutes resistances R5, R6 for R1, R3 respectively and brings about other circuit changes. Relay SA(i) energizes, connects up the signal repeating relay TC, and closes the discharge circuit for the condenser QC. After 4 seconds the tube NT strikes and relay C operates CA which locks and releases SA by connecting in its opposing winding SA(ii). Relay TC falls back, completing the first mark, and G pulls up and associates the tube NT with the timing circuit QF, R6. After 1 second, the tube NT again strikes and relay F disconnects CA, G, SA(ii). Relay SA therefore reoperates and starts the transmission of a second mark. The cycle of operations continues until the switch TR is reversed. The Provisional Specification refers to Specification 334,205, [Class 40 (iv)].