GB376820A - Improvements in or relating to telegraph systems - Google Patents

Abstract

376,820. Code telegraphy. STANDARD TELEPHONES & CABLES, Ltd., GROVE, S. H., FEDERICI, M. E., SANDEMAN, E. K., and CURRAH, L. E., Columbia House, Aldwych, London. April 16, 1931, No. 11266. Addition to 353,515. [Class 40 (iii).] Lost dots are reinserted at a receiving station by means of a thermionic flip-flop device of the kind shown in Fig. 4 of the parent Specification and at the top of the accompanying Fig. 1. The present invention provides means A, B for bringing the inserted dots into phase with the received signals. Locally generated impulses of the form f, Fig. 2, are applied at terminals F, Fig. 1. The frequency of these impulses is double the dot frequency, and the connections are such that in the absence of received signals the valves V3, V5 become operative alternately, one being jammed while the other is operative. The impulses f therefore pass alternately through the pairs V3, V4 and V5, V6, so that the pulses of current through condensers C1, C2 respectively are represented by graphs c1, c2, Fig. 2. To produce this result the alternating pairs of valves interact with the flip-flop device, which feeds their input terminals through leads p1, p2, and is fed by their output terminals through leads q1, q2. The output of the flip-flop device at terminals O in the absence of received signals is shown at o, and comprises a succession of dots. Signals whose original form was a, Fig. 3, arrive in the distorted form b through terminals L and are applied to resistance R4. So long as their strength lies within the limits x, a; the system continues to insert dots ; but the stronger signals J, H, due to blocks of two or more impulses of the same polarity, overpower in R4 the effect of the locally-generated impulses and delay the operation of the valves V1 .. V6, which afterwards resume work in the correct phase. The impulses of current through condensers C1, C2 and at terminals O, as affected by signals b, are shown at c<1>1, c<1>2, o<1>.