Patent GB-644922-A (GB)
Title: Electronic code sender for start-stop telegraph signals
Inventor: DUNN ROLAND HARRIS
IPC: H04L13/14
Filed: 1947-09-17
Abstract: 644,922. Type-printing telegraphy; thermionic distributers. STANDARD TELEPHONES & CABLES, Ltd. Sept. 17, 1947, No. 25388. [Class 40 (iii)] A start-stop telegraph transmitter comprises a chain of cold - cathode discharge tubes composed of a start tube, a stop tube and for each code element both a space and a mark tube, and means for causing the start tube, the correct one of each code pair, and the stop tube to conduct sequentially to transmit a desired character. In the normal condition a closed chain of cold-cathode tubes 22, of which there is one for each character, is tiring sequentially under the control of alternate (e.g. odd) impulses from a suitable generator 26, and the tubes 21 of each character circuit such as 18 ... 21 are conducting. So long as any counting tube 22 is conducting the anode current holds a transmit relay 27 in the mark position. When a particular character is to be transmitted a corresponding contact 51 is made, e.g. by depressing a character key and a condenser 50 discharges and fires the first associated character tube 18, extinguishing the character tube 21 and placing a positive potential on the control electrode of a start tube 30. This tube is arranged as the final tube in a gating circuit as described in Specification 636,700, [Group XL (c)], and is primed only when firstly tube 18 fires, and secondly the counting tube connected to the latter (23 as shown) also fires. The start tube 30 is then fired by the next, even, impulse from the generator 26, extinguishing the counting chain tube 23 to stop the chain and by its anode current operating the transmit relay to space. The next character tube 19 is similarly primed by the operation of both tubes 18 and 23 and also fires on the next, even, impulse, applying a partial positive bias to the particular five out of five space tubes 32 ... 40 and five mark tubes 31 ... 39 to which it is connected over leads X, which connections are arranged according to the five-unit code of the character represented by the depressed key. The selected tube of the first code pair 31, 32 is thus primed by the additional firing of the start tube 30 and on the next even generator impulse this code tube fires, operating the transmit relay to mark or space accordingly. Each of the code tubes 33 ... 40 which are connected to the character tube 19 now fire in turn under control of the impulse generator 26, and finally the stop tube 41 fires. The operation of this tube, in addition to tube 19, primes the next character tube 20 which fires on the next even generator impulse, extinguishing tube 19, and priming the distributer tube 24 which fires on the next, odd, impulse and starts the counting-chain again. The final character tube 21 fires on the next even generator impulse, extinguishing tube 20 and thus returning the circuits to normal. By employing thirty-two counting tubes 22 and thirty-two character circuits 18 ... 21 the usual character and function signals may be transmitted. Specifications 566,156, 636,667 and 636,668 are referred to.