Patent GB-666699-A (GB)
Title: Improvements in or relating to telegraph transmitters
Inventor: GOULD WILLIAM FREDERICK
IPC: H04L25/45
Filed: 1948-10-08
Abstract: 666,699. Code-telegraphy; thermionic valve and like distributers. STANDARD TELEPHONES & CABLES, Ltd. Nov. 8, 1949 [Oct. 8, 1948], No. 26287/48. Class 40 (iii). [Also in Group XL (c)] In a telegraph transmitter for mark-space signal combinations, the combination is set up by firing appropriate ones of pairs of cold-cathode discharge tubes, the voltage wave representing the signal combination being generated in dependence of the particular tubes rendered conducting and upon the operation of a distributer chain of cold-cathode discharge tubes fired in regular timed sequence by a source of timing impulses. In Fig. 1, the code combination set up on five contacts 6-10 is transferred to five twocondition devices 1-5 upon closure of a contact 12. Each device comprises a pair of cold-cathode discharge tubes T1 (space) and T2 (mark) interconnected with a common anode load R4 so that the firing of one tube extinguishes the other. Initially the devices are all set with the mark tube conducting and the circuits extending through the closed contacts of the series 6-10 cause selected space tubes to fire. Simultaneously with the closing of contact 12, a contact 14 sets into operation a distributer comprising a chain of cold-cathode tubes T3-T10 so interconnected and having a common anode load R6 that the firing of one tube extinguishes the preceding tube and primes the succeeding tube. A source of 1 millisecond pulses operating at a frequency of 50 per second is applied via condensers C4 to trigger the tubes in sequence, the circuit to the first tube T3 extending through contact 14. The voltage variation representing the signal combination appears on line 15 which is given a steady marking potential unless a space is transmitted. As each distributer tube fires its cathode potential raises the bias on a rectifier X3 and allows the potential at the cathode of the space tube of the associated twocondition device to appear on line 15. In this manner, dependent on the combination of space tubes fired, mark or space potentials in accordance with the code set up on contacts 6-10 appear in sequence on line 15. A connection through rectifier X1 from the first tube T3 provides the start space signal. The twocondition devices are reset at the end of the signal with mark tubes conducting by connections extending from the pulse generator via condensers C6 and from distributer tube T9 via rectifier X4. The last tube of the distributer T10 is connected through resistance R8 to condition the first tube T3 to fire again and restart operations upon subsequent closure of contacts 12 and 14. Owing to the presence of CR networks in the cathodes of the various tubes, the voltage variation on line 15 is in the form of a series of exponential impulses. A valve relay circuit (see Group XL (c)) comprising valves V1-V5 converts these impulses into square-topped impulses which appear on mark and space lines 16, 17. Valves V3 and V4 are connected as a direct coupled " flip-flop " circuit and are triggered from one condition to the other by impulses from the 50-cycle/sec. source under the control of values V1 and V5 in dependence of the impulses on line 15 which are applied to the grid of valve V2. In a modified transmitter, Fig. 2 (not shown), the tubes T4-T8 of the distributer are each replaced by a pair of tubes, one tube being controlled by the mark tube of the corresponding two-condition device and the other by the space tube. The distributer is triggered in sequence as in Fig. 1 but with only one tube of each pair firing as determined by the setting of the twocondition devices. The mark tubes of the distributer pairs connect with one output line and the space tubes with another line. In this manner the mark and space elements of the transmitted signal appear on separate lines. Specifications 613,137, 636,669 and 644,922 are referred to.