GB390542A - Improvements in or relating to electrical signalling systems - Google Patents

Abstract

390,542. Code telegraphy. ELECTRICAL RESEARCH PRODUCTS, Inc., 195, Broadway, New York, U.S.A.- (Assignees of Burton, E. T. ; 97, Cypress Street, Millburn, New Jersey, U.S.A.) Oct. 13, 1931, No. 28413. Convention date, Oct. 23, 1930. Addition to 312,338, [Class 40 (iii), Telegraphs, Electric]. [Class 40 (iii).] " Impulse coils " having high permeability over a narrow range of ampere-turns, as described in the parent Specification, are combined with thermionic amplifiers for squaring wave-form and eliminating small disturbing currents in two-element (+, -) or threeelement (+, 0, -) code. The curve in Fig. 3 represents signals received at terminals 10, Fig. 1, the transformers being ineffective, owing to core-saturation, except at signal strengths lying in the range between lines A and B. The rise from a to a<1>, Fig. 3, sets up a brief impulse p, Fig. 4, in transformers 12 and makes the grids of valves 17, 27 momentarily positive and negative respectively. During the brief impulse, condenser 30 rapidly acquires a positive charge through valve 17 which then blocks up again so that the charge remains on the condenser. Valve 33 therefore passes current as at x, y, Fig. 5. When the signal passes from b<1> to b, Fig. 3, a reverse impulse q is applied to the valve-grids by transformers 12. Valve 27 consequently opens for long enough to discharge the condenser 30, so that the grid of valve 33 becomes negative and current in the output circuit 11 falls to the value z, Fig. 5. In a modification, Fig. 6 (not shown), three signal elements +, - and 0 are employed. The valve 33 is then governed by two condensers 30 in series, each condenser being governed by a pair of valves like the pair 17, 27 in Fig. 1; and the transformers are biassed so that impulses are produced not when the signal crosses the zero line G, Fig. 7, but when it crosses either of the regions CD, EF. So long as the signal is in the middle region DE the output current is zero, and hence small signal-fluctuations due to disturbing currents are eliminated. The signal shown in Fig. 7 is regenerated to the form shown in Fig. 10. The condenser 30 may be dispensed with and a single impulse-coil transformer 12 feeding a flip-flop pair of resistance-coupled valves employed, Fig. 11 (not shown) ; or two pairs of such valves may have their outputs connected in series so as to reshape signals as shown in Figs. 7 and 10. In a modification, Fig. 13, only three anode batteries are required, and the positive and negative potentials applied to grid of valve 33 are both determined by the same battery 171. The pair of valves 147, 157 are interconnected through resistances 139, 140, so that when one is passing current the other is blocked ; and the pair 167, 177 are similarly interconnected. When the, signal crosses the region CD at a, Fig. 7, transformer 164 is unaffected owing to its bias, but impulse p, Fig. 8, from transformer 142 blocks valve 147, destroying the potential drop in resistance 139. Valve 157 therefore opens, setting up in resistance 140 a potential drop which opposes that in resistance 150 so that the grid-potential of the output valve 33 falls to zero as at x, Fig. 10. When'the signal crosses region EF at a<1>, biased transformer 142 is unaffected but an impulse p<1> through transformer 164 opens valve 177. Valve 167 closes, the potentialdrop in resistance 150 ceases, and the gridpotential x<1> of valve 33 is then negative as determined by the potential drop in resistance 140. At the point b<1>, impulse q<1> through transformer 164 closes valve 177 and gridpotential y<1> of valve 33 falls to zero ; while at the point b, impulse q through transformer 142 opens valve 147 and the grid-potential of valve 33 is the positive potential drop y in resistance 150. Glow discharge lamps may be used instead of valves.