US1537682A - Telegraphic receiving system - Google Patents

Description

' May 12, 1925. I 1,537,682

G. KRAUSE TELEGRAPHIC RECEIVING SYSTEM Filed Oct. 26, 1920 2 Sheets-Sheet 1 May 12, 1925.

G. KRAUSE TELEGRAPHIC RECEIVING SYSTEM 2 Sheets-Sheet 2 Filed OCt. 26, 1920 Patented May 12, 1925.

UNITED STATES PATENT OFFICE.

GEORG KRAUSE, OF BERLIN, GERMANY, ASSIGNOB T0 SIEMENS & HALSKE, AKTIEN- GESELLSCHAFT, 0F SIEMENSSTADT, NEAR BERLIN, GERMANY, A GERMAN COB- POBATION.

TELEGRAPEIC RECEIVING SYSTEM.

Application filed October 26, 1920. Serial No. 419,778.

(GRANTEDUNDER THE PROVISIONS OF THE ACT OF MARCH 3, 1921, 41 STAT. L, 1313.)

To all whom it may concern:

Be it known that I, Gnone KRAUsE, a citizen of the German Empire, residing at Berlin, Germany, have invented certain new and useful Improvements in Telegraphic accordance with the increase in length of the line as well as the increasing distortion of the current curves are so troublesome that it is impossible to go beyond a certain len h of line, the damping caused by the line ecoming so great that the amplitudes of the current curves do not sufiice any more to actuate the receiver. If the current impulses tollow each other in rapid succession, the shorter impulses do not fully develop, because they do not attain the value resulting from the transmitting voltage and the total resistance.

In order, to amplify such extremely small amplitudes of the current impulses it suggests itself to connect in series with the receiver an amplifying device of such ampl fying power that even the smallest amplitudes are amplified sufliciently to actuate the receiver. however the disadvantage that very great amplitudes arriving over the line are amplified to the same degree as the weaker ones, thus causing the formation of secondary amplitudes of such magnitude that the adjustment of the sensitive receiver is very unfavorabl aflected. For this reason in such devices eretofore used the smaller amplitudes may be amplified only to a limited degree.

An amplification of such kind has In the receiver system according to the present invention provided with an amplifier for the transmitting currents the small amplitudes can be amplified sufiiciently to secure the actuation of the receiver without this latter being endangered by the great secondary amplitudes produced by stronger current impulses. This is effected accordmg to the present invention by employing an amplifier having its current amplitudes limited in such a way that tlroseamplitudes which extend to its current limits, suflice to secure the actuation of the receiver, while the secondary amplitudes transgressing such limits are cut otl at the permissible current limits.

Amplification of this sort can be carried out in an especially efiective manner with the aid of glow cathode relays with pure electron emission, whose current limits can easily be predetermined by selecting suit able potentials for the electrodes, a suitable surface area and temperature of the glow cathode. One may however employ as well other vacuum tube amplifiers and devices of a difl'erent kind which may for instance be connected with current limiting means such as-a highly tempered iron wire, or devices provided with mechanical current limiting means such as for instance a Brown relay provided with stops.

Owing to the fact that a receiving system according to the present invention renders very great amplification possible, a steep- Figure-2 shows a receiving system according to the invention to be used in connection with a double line,

Figure 3 shows the connections for keeping the closed circuit current off the relay,

Figure 4 shows a transformer, and

Figure 5 shows a condenser connected in series with the amplifier,

-Fi ure 6 shows a system embodying two amplifiers connected in series.

Referring to Fig. 1 of the drawings, the

effect of the amplifier can be ascertained from the forms of the curves I, II and III. Supposing a signal composed of positive and negative current impulses be sent out in the form I and to arrive at the receiving station in the distorted form of curve II, this signal when amplified would assume the form of the dotted curve III. Thus stronger and weaker amplitudes alternating with each other influence the receiver in a difterent degree. According to the present invention, an amplifier is employed whose secondary current limits are reached at 9,, g,, so that even in case the grid voltage should rise higher, no greater current is supplied to the receiver, that is to say, all amplitudes passin beyond that point are cut off. There ore the signal transmitted secondarily by the amplifier assumes about the form of the curve III drawn in full lines which is practically identical with the curve I. Thus a certain regeneration of. the original signals takes place, especially in the case where a very high degree of amplification is resorted to, which may be done quite safely. Y I

A receiving system according to the present invention designed for a, double line is illustrated in Fig. 2. In receiving telegraphic signals consisting of direct current impulses it is desirable in many cases to preserve in the received signal the form of the impulses arriving at the receivingstation as truly as possible. In such telegraph systems where a cathode amplifier tube is connected in series with the receiver at the receiving station it is not possible to attain this end in a simple way, the customary inductive coupling as shown for instance in Fig. 4 exerting a strongly distorting action upon the direct current impulses arrlving at the end of the line. Even a direct connec tion of the line with the grid and the cathode of the amplifier tube does not furnish the result desired on account of wave reflections. The system illustrated in Fig. 2- allows to obtain a true reproduction of the si nals arriving at the end of the line by an o mic resistance of suitable dimensions bridged across the line, such resistance at the same time serving to adjust the zero potential of the grid.

This continuous current grid potential is mamas preferably chosen such that it corresponds to the middle of'the linear or straight portion of the characteristic curve of the am- ,plifier.

As, shown in Fig. 2, a cathode ray tube V is provided having a hot cathode or filament F, a grid G and a plate or anode P, the filament F being heated by a battery A. The ends of the line connected-to the grid circuit FG\are bridged by a resistance r, the direct current for the zero potential of the controlling grid being supplied from a battery b through aforesaid resistance. The secondary or anode current of the tube may serve to actuate some suitable receiving device such as a polarized relay R whose contacts are marked in the drawing. The same system might of course be applied to single conductor lines as well, in which the other conductor is formed by the ground.

The secondary current impulses generated by this system further allow the use of any suitable kind of receiving device since the arriving impulses resemble in form the transmitted ones.

Assuming the adjusted armature, resting against one stop contact, is thrown against the otherstop contact by an incoming positive wave, then it will be thrown again against the first contact at the end of this wave and remain against this stop contact, while the following negative wave comes in and it will be thrown against the second stop contact at the end of the negative wave, viz. the beginning of the' next positive wave, as the end of one wave coincides with the be ginning of the following wave.

If it is desired to keep the anode continuous current component, resulting from the battery grid potential, away from the relay, this maybe effected by means of the system illustrated in Fig. 3 where the receiver R receives its current from the amplifying device over a capacity K, a resistance R being inserted in the anode circuit in parallel with the receiver. B is the anode battery. With such a device the relay R is only affected on changes, but as positive and negative waves are succeeding one another, the armature is only reversed once for each impulse. In order to obtain the truest possible reproduction of the signals through the secondary current impulses care must be taken to make the time of dying away of the discharge current of the condensor as long as possible in order to prevent it from falling to zero before the end of the signal. This may be obtained by a sufliciently large capacity K, and a sufiiciently high resistance R.

If a polarized relay is used-as receiver in the system illustrated in Fig. 3 the time of dying away of the capacity discharge current can be chosen such that there result only very quick and short current impulses which actuate the relay whose armature is reversed in every instance by the impulses following each other.

In high speed transmission over very long lines it may happen. even with pupinised lines, that owing to the great distortion of the signals short current impulses such as dots following or proceeding a dash are not developed fully, the grid voltage not going down to the battery current potential ofthe grid between two dash-signals. In such a case the arriving signal has the form of a curve as shown at II (Fig. 1). Receiving systems as shown in Figs. 2 and 3 will not serve for signals of such character. The curve would have the form of the curve drawn in'dots and dashes at III (Fig. 1) and owing to the limitation of current of the amplifier tube it would furnish the anode or secondary current m n p and in consequence thereof would cause only a single contactmaking of the relay instead of five. I

This drawback is obviated by connecting in series with the amplifier tube a transformer U, as shown in Fig. 4. or condensers 2 as shown in Fig. 5 in both of which the remainder of the tube connections may be as shown in Figs. 2 or 3. In case a transformer is used the induced current will at each reversal of current pass through zero and will then increase in an opposite sense. If condensers are provided, at the reversal of current, charges and discharges will alternate. In consequence thereof the grid fluctuation will pass at each reversal of current through the battery potential of the grid and all the amplifiedcurrent alternations and current signals respectively thus attain the zero line, respectively the amplitude of the continuous current amplitude, resulting from the battery grid potential so that no signal is suppressed. v 7

The use of transformers and capacities further involves the advantage that in the partial transformation of the impulses the points and corners which coincide according to curves I, II and II (Fig. 1) and correspond to the reversals of current, also coincide with the lines of intersect-ionof the transformed impulses and thezero line. In the case of high amplification, therefor, ow-

. ing to the steep rise of the amplified current,

the receiving relay is actuated almost exactly in conformation with the corners, this being of paramount importance for all devices working in synchronism.

If a plurality of amplifying devices connected in series are used, the connection illustrated in Fig. 6 is preferably employed. The first amplifying tube is selected so that all impulses of the amplified cable end current lie within the current limits of the amplifying tube. The first amplifier tube V, is coupled with the second one V over a capacity K, and a resistance R which may be an inductance. In the secondary circuit of the first amplifier tube is inserted a resistance R The current fluctuations in its secondary circuit cause fluctuations of voltage at the resistance R, and these fluctuations are transferred over the capacity K to the grid of the amplifier tube V The grid of the latter receives its direct current potential from a battery I), over the resistance R which must be of sufiicient size to prevent a premature dying away of the condenser charge. The receiver B may be connected to the secondary system of tube V in a manner similar to that shown in Fig. 3, i. e.. by connecting it to the ends of resistance R by way of condenser K All the arrangements described may of course be used also in single core cables with earth return line. They may further be employed with advantage for transferring the signals from one cable section to the other.

I claim 1. The method of receiving telegraphic signals formed of direct current impulses which consists in highly amplifying the signals to form steep current curves and suppressing the apexes of such secondary amplitudes as might disturb the operation of the receiver before the said amplitudes reach the receiver, in limitin the current of saturation of the amplifying tube for amplifying the signals so that the apexes-of said secondary amplitudes are cut off to obtain substantially rectangular current curves in said receiver.

2. Receiving system of the kind described comprising in combination a cathode ray tube having its primary circuit connected to the line, a receiving device connected in series with the secondary tube circuit, a secondary current in said tube being limited by the choice of an appropriated current of saturation, so that the apexes of such secondary amplitudes are cut oil, to obtain substantially rectangular current curves in said receiver.

3. A receiving system of the kind described comprising in combination an ohmic resistance placed across the ends of the receiving line, a cathode ray tube having its grid circuit connected to said resistance, a direct current source for impressing a potential to the grid, means for conducting also the direct current derived from said source over said resistance, said cathode tube adapted to amplify fully the lowest incoming waves, an ohmic resistance inserted in the secondary or anode circuit of said cathode ray tube, a second cathode ray tube having its grid circuit connected to the secondary system of said first mentioned cathode tube, a source of direct current potential applied to the grid of said second tube and a resistance in circuit therewith, a receiver connected to the secondary system of said second .llt)

tube, the current of saturation of the said second tube being limited so as to cut off the apexes of such secondary amplitudes which might disturb the work of said receiver, a resistance inserted in the anode circuit of said second tube having the receiving apparatus connected to its ends, and a capacity inserted in the connection between the anode circuit of said first mentioned cathode ray tube and the grid circuit of said second cathode 10 ray tube, a capacity being also inserted in circuit with aforesaid connection of the receiving apparatus.

In testimony whereof I affix my signature.

GEORG KRAUSE.

Images