US2238028A - Telegrad - Google Patents

Description

Apl 15, 1941.

H. l.. BARNEY ETAL TELEGRAD Filed July a, 1959 4 Sheets-Sheet 1 H. L. BARNEV /NVENTORSI U.$. BERGER AE'. MELHOSE 'ATTORNEY April 15, 11941.f H. L BARNEY Erkl. 2,238,023

TELEGRAD Filed July 8, 1959: 4 Sheets-Sheet 2 ATTORNEY April 15, 1941. H. 1 BARNEY Erm.

TELEGRAD Filed July 8, 1939 4 Sheets-Sheet 'o' HQL. BAR/ver /Nl/N TOR$= as. BERGER A E. MELHOSE ATTORNEY April 15 1941. H. i; BYRNEY TAL 2,238,028

TELEGRAD Filed July 8, 1939 4 sheets-sheet 4 ksmo/va sla/VAL oPEnAr/o/v RELEASE or 6.4m o scRfAsE/e i Y .Kops/u TloN 0F RELAys 7oz 7/ LA. o z V) Ivo/ss rHnEsf/QLD AND sENs/r/v/rr snm/c ar wmv mmh-essex I F76. 6 l oPERA/ON l l RELEASE or aA//v oscense@ r g LOPE/M rloN 0F RELArs 7a s 7/ 2 k Il [me-AK sla/VAL No/ss @nsf/ow AND' 1 yg 12v/rr seg/ N535 aygcfgqgl TIME 1 @ARA/Er /M/ENTORS: as. BERGER y Af. AfL-Hose secondly,` disable the enabling circu Patented Apr. 15, 1941 TELEGRAD Harold L. Barney and Uriah and Alfred E. Melhose, St.

ors to Bell Telephone rated', New York, N. Y.,

S. Berger, New York, Albans, N. Y., assign- Laboratorle's, Incorpoa corporation of New Application July 8, 1939, Serial N0. 283,368

(Cl. PIB-86) 1.9 claims.

This invention relates to communication systems and particularly to telegraph systems operating over channels subject to iniluences giving rise to great variations in the strength and quality o1' signals received.

The object o1 the invention is to regulate received signals Iin such manner as to deliverto receiving apparatus signals of uniform amplitude and length.

A feature oi' the invention is a telegraph gain regulating amplifier-detector which will hereinafter be termed a telegrad. 'I'he object of this device is to regulate telegraph signals received over a mutable link such as a badly fading radio circuit and to render such signals uniform in strength. A feature oi this circuit is fast iorward-acting gain increasing circuit, a fast baci:-

ward-acting gain decreasing circuit and a gain increase disabler. The telegrad has features of similarity to the well-known vogad (voice operated gain adjusting device) shown, for instance, in Patent 1,853,974, granted April l2, 1932, to Hogg et al., Patent 1,936,658, granted November 2u, 1933, to Bjornson etal., Patent 2,012,810, granted August 27, 1935, to S. Doha, and Patent 2,156,622, granted May 2, 1939, to S. Doba..

The telegrad, however, is designed to be extremely quick acting in comparison to the vogad and, for this reason, novel means have been incorporated in the new circuit in order that proper control of the device may be exercised. For example, both these devices iemploy a gain increaser disabler for the purpose oi halting the eiect of the gain increaser when it has increased the gain of a vario-repeater to a given point. Due' to the highalternating currentvoltages at the output of the gain increaser circuit. it is not possible to use a mere relay contact to disable the increaser circuit output. Hence, a feature oi this circuit is a two-step device for iirst cutting oi the energizing path to the gain increasing means and secondly and thereafter to reduce the enabling bias of the gain increasing means.

Expressed in another manner, the gain increaser circuit employed herein is to a certain extent automatic and comprises two parts, an activating circuit and an enabling circuit. The activating circuit starts it into operation with the enabling bias applied and the disabling means acts to first disable the activating circuit and to In both the telegrad andthe vogad, the gain o1' the vario-repeater is controlled by the potential of a condenser. It is, therefore, necessary when this condenser has been charged to a cerloss and, subsequently,

selves for operating the disabler.

` high loss in the circuit and in another condition inserts a negligible loss in the circuit while maintaining an approximately even electrical constant condition therein. This well-known device, shown in Patent 1,749,851, granted March 11, 1930, to H. C. Silent, renders the circuit open for transmission of alternating currents in the low loss condition and practically opaque for such transmission in the high loss condition. The output of this crossed coil device is connected between a source of positive potential and a cold cathode gas tube in the charging circuit of the gain regulating condenser circuit so that energy traversing the crossed coil device will actuate the cold cathode gas tube and cause a flow of direct current for charging thecondenser. The action is stopped by first changing the condition oi. the crossed coil device from a low to a high reducing the positive potential in the condenser charging circuit. Thereby. the gain regulating condenser is left at a desired potential which may further be regulated by the gain decreaser circuit.

In accordance with another feature of the nvention, economy of apparatus and insurance against dierence in sensitivity between diiferent circuits is achieved by operating the gain increase disabler from the signal circuit which is the final output of the telegrad, or, in other words. using the direct current signals them- In the vogads, the gain increase disabler was part of the vogad and, therefore, required certain apparatus in the nature of an amplifier and detector for operating the relay means which performedthe function of disabling the gain increaser circuit. The telegrad, however, may be considered as the combination of a vogad and an amplier-detector for operating a signal circuit in which the gain increase disabler of the vogad is operated from the signal circuit beyond the ampliiier-detector. By this means the expense of providing the usual ampliiier-detector of the gain increase disabler is saved. Since the disabler is now Worked by the final signal circuit, exact synchronism o1' the ture of this circuit is a pair of relays, the first 'of which is directly responsive to the direct current signals from the amplifier-,detector and the second of which is responsive to the first. Between the rst and second of these relays there is a. delay circuit so that the second does not move its armature until a specified time after the energization of the first. Through a circuit controlled by the armatures of both these relays. the output signals are controlled at their beginning by the second relay and at their end by the first relay. A feature of the invention, then, is a signal timing circuit which effectively shortens the output signals by cutting oil a portion of the beginning of each.

Another feature of the invention may be said to reside in the method of transforming varying strength alternating current signals into equal length direct current signals which consists essentially of three steps; flrst,`the transformation of the different strength alternating current signals into uniform strength alternating current signals; second, the transformation of such uniform strength alternating current signals into direct current signals, and, third, the adjustment of the length of the direct current signals to the length of `the original signals. The intermediate stage signals are spoken of as uniform strengthi signals to denote the fact that regardless of the strength of the original signals, such intermediate stage signals are always approximately the same. The term "uniform does not apply to the form of the intermediate signal throughout its length for such signal is not strictly uniform in that sense. Actually, due to preliminary filter bulldup and tail-off and due to the extreme rapidity of the gain increaser action, each signal has what may be termed an enlarged head, a major body portion of approximately uniform amplitude, and a. gradually decreasing and elongated tail end.

The gain increaser acts so rapidly that by the time the disabler can operate, and due also tov gives a characteristic enlarged head effect to the signals.

Where the signals are of the order of twenty milliseconds in length, the enlarged head is of the order of five milliseconds in length and where' the tail end of the signal is elongated in the order of five milliseconds, the signal is compensated by cutting off about five milliseconds of its head.

It will then be realized that the regulated signals will be displaced somewhat in time, but, since this displacement is uniform for all signals, the usual orientation means may be used for purposes of synchronization. Another feature of the invention, then, is the combination of a telegrad comprising a fast-acting vogad, an amplifier-detector beyond the vogad controlling the gain increase disabler of the vogad and a pulse chopping circuit and an orientation means for insuring the correct operation of telegraph receiving mechanism by signals ba'dly distorted in respect of their strength.

The drawings comprise four sheets. The first contains Fig. 1 illustrating by a general schematic diagram the manner in which the present invention lits into a comprehensive communication system.

Fig. 2 is a circuit diagram showing the telegrad in detail. 'I'his diagram is schematic to the extent that in each vacuum tube the heater element or filament is merely indicated and the actual connections thereto are not shown since the method of making such connections is well known.

Figs. 3 and 4 are explanatory diagrams illustrating the transition of a signal from fthe signal delivered to the telegrad, the intermediate stage signal and the direct current signal delivered to the signal receiving apparatus by the telegrad. Fig. 3 shows a strong sign-al and Fig. 4 shows a weak signal.

Figs. 5 and 6 are theoretically devised graphs showing the time of operation of the various parts of the circuit whereby the intermediate stage signals are properly formed.

Fig. 1 is a general schematic of the system in which the telegrad, subject of the present invention, is employed. A speech path I leads tc a hybrid coil 2 from which a path 3 for outgoing speech leads to a vogad 4. The outgoing speech then passes through a. transmitting suppressor 5 and by means of an amplifier-detector 6 operates a chain of relays 'I here labeled as"voice operated switching circuit. This voice operated switching circuit controls a transmitting singing suppressor S so that the outgoing speech can pass from the transmitting suppressor 5 through the delay and amplier 8 and the transmi-tting singing suppressor 9 to the hybrid coil Ill. From the hybrid coil Ill the speech reaches another hybrid coil II and thence goes through the radio transmitter I2 to an antenna I3. Through radio transmission the speech will be received at some distant point and for purposes of explanation it will be assumed that the distant point has a receiving circuit similar in all respects to the lower part of Fig. 1. The speech therefore enters antenna I4, passes through a radio receiver I5 and a repeater i6 4to a hybrid coil I1. From the hybrid coil I'I the speech goes into hybrid coil I8, thence through the receiving singing suppressor I9, the receiving repeater 20, a low-pass filter 2I and a path 22 to a hybrid coil such as 2, whence it goes to the receiving subscriber over a line such as i.

The voice operated switching circuit 1 controls a control tone enabler 23 so that a source of control -tone 24 is passed through the control tone filter 25 to `the hybrid coil II and thus accompanies speech. The voice operated switching circuit I also controls a switching point leading from the receiving switching circuit 26 at the same terminal to the transmitting suppressor 5 so as to open this circuit during the periods that speech is going out from line I to antenna I3. During this time the voice operated switching circuit 1 also controls the telegraph control circuit 21 to stop the action of the telegraph transmitting circuit.

At the receiving end the control tone'with the usual modulation of the carrier frequency coming in over antenna Il is demodulated in radio receiver I5 and passes through hybrid coil I'I and thence through a telegraph band elimination lter 28 and into a control tone amplifier and lter 29. This operates the receiving switching circuitl 2l which performs several functions as follows. First, the receiving switching circuit 25 controls a normally open circuit between the telegraph band elimination filter 28 and the reeration.

'with side bands about 'l5 celvlnc switching circuit 28 including a speech ampliiler I0. This is provided so that when control tone is first received the receiving .switching circuit 2t will be operated thereby and then held operated thereafter by speech currents flowing through the amplifier I0.

The receiving switching circuit also controls the receiving singing suppressor I8 to open up the speech path. The receiving switching circuit it also controls a normally closed path between the band-pass filter il and the telegrad 32 so that while speech is being received the telegrad il `will be disabled` At the same time, the recelving switching circuit 2| controls the switching relays for two telegraph channels 33.

During pauses in the speech, either when the subscriber' at the distant end is talking into channel l or during the time when the subscriber on channel i pauses during his talk out over the antenna i3, the telegraph apparatus u shown in the upper part of the figure is in op- 'llhis comprises perforator. 3l and 33 Woridny, respectively, into tape transmitters I8 and il' and thence, into rotary distributor 3i. ltotary distributor t8 works through the control circuit il which exercises control over the telegraph signal suppressor 39. A source o1' telle-I graph signal tone is supplied by the telegraph signal oscillator 40 and through the action ol the telegraph signal suppressor 3l under control oi' the control circuit 2l sends telegraph signals into the hybrid coil I0, thence through the hybrid coil li and out over the radio transmitter I3.

llt the distant end these telegraph signals. in the iorln of spurts of alternating current of the usual iorin oi a carrier of the oscillator frequency cycles wide caused by the modulation of the carrier by the telegraph transmitter are received over antenna i4 by the radio receiver l 5 and thence through the repeater to pass through the hybrid coils I'l and Il to the band-pass filter 3l. Thereafter, the signals enter the telegrad k32 and are converted from raryinal strength alternating current signals to uniiorin strength direct current signals of lprenoticaily the same length at which they were recelved over the antenna I4. These direct current signals then pass through the switching relay circuit il and the rotary distributor 4| to the tivo printers lil and 43. ol telegraph signals the receiving switching circuit it is unoperated and the speech path is hloclred oil" by the receiving singing suppressor it. .il line ifi schematically represents a means tor lrecping chrouisin with the distant rotary distributor 6l. 'lire rotary distributor 38 and the rotary clistrihutor lil at the same terminal may or may not be irept in synchronism.' In actual practice they generally are lrept in synchronism for reasons haring to do with the cost of synchronizing apparatus, 'but from an operating standpoint it is only necessary that the rotary distributors form` ing part ofthe same channel beY kept in synn chronisin.

'The telegrad 32 `is shown in detail in Fig. 2. Signals coming from the band-pass illter 3i pass through a varia-repeater consisting of two stages, first, a copper-oxide vario-losser pad and, secondly, a `push-pull varlable-mu amplifier stage. The signals pass through a transformer 5U and'thence through the copper-oxide variolosser pad to transformer 5I. From transformer 5| they pass in push-pull relation through twoy variable-mu suppressor-gridl pentode tubes 82 During the reception the rotary distributor 38 in exact syn and Il tofa transformer I4. The copper-oxide vario-losser pad comprises four copper-oxide rectiers 55, B8, il and Il connected in a bridge circuit across the outer terminals of transformers 50 and 5| across. The outer apex points of this bridge are connected in one case to a potentiometer B0 be tween plus battery and ground, and in the other case ot themid-point of the primary oi transformer I4. The current iiowing in the coppermilde bridge is then a function of the plate currents flowing in tubes t2 and 63 sin the plate current drop across resistance 8l is balanced against the potential derived from potentiometer it. The larger the plate current flowing through resistance, the smaller will be the direct current flowing through the copper-oxide bridge. The important clement in this vario-repeater is a condenser 6I. The potential oi the upper plate ofv this condenser determines the gain to the signal. The gain of the vvario-ropeater is increased by raising the positive charge on coudenscr 6l and is reduced by a corresponding reverse action adjustment. Through the use of a potentiometer 82 the potential oi' the upper plate of condenser il may be kept at such a point during idle periods that the variorepcater is ect at mid-gain g AThe signals going out from transformer bil pass through a suppressor-grid pentode tube H3 and thence to a. hybrid coil 84. IThe output oi this hybrid coil works into a transformer and thence through a suppressor-grid pentode tube 8b, acting as an amplifier, to a transiorlner 6l and thence to a full wave rectliier tube til. Under normal conditions, that is, inthe condition oi a spacing signal, a suppressor-grid pentode tube 68 is so adjusted by the potential on the naidpolnt of the secondary of transformer tl that current flows from the plate oi' tube tu through the neutral relay lll and the upper winding' oi relay li, holding them in the positions shown. When a marking signal is transmitted then a direct current voltage is produced acrossthe diode resistance "l2 and the negative voltage re duces the plate current from tube 69 to the point where relay 'Il releases and the biasing current in the lower .winding oi relay 1i drives this relay to its marking contact. When relay 'Il moves from. its spacing contact, a short circuit on hangover condenser "i3 is removed and this condenser in time is charged by the positive battery connected through the upper winding of relay lt. 'this charging current holds relay 'll on its spaclng contact for the hang-over period. Thereafter, as the biasing current through the lower winding of relay 'lll becomes effective and relay 14 moves to its marking contact, a circuit is closed trom ground through the armature of relay ll and its marking contact, thence through the armature oi relay to the receiving distributor lead l5.

Since the telegrad is used at the output of a selective dlter 3|, the length of the pulses reach .ing the input is longer than the signal transf mitted. Since relay 1I follows the signals at the input of the telegrad, the circuit including relays ll and 14 and the hang-over condenser 13 is provided tov regulate `the length of the" pulses going out on lead l5 to the length oi the pulses before they pass through the band-pass lter 3ll y In general terms, then, alternating current lmpulses which may vary from strong signals to very weaksignals over a range of some 45 decibels are converted bythe vario-repeater into a1- with a pure resistance 58 bridged there' 'M and its marking contact`- ternating current signals of a practically uniform amplitude, These signals then pass through an amplier-detector` and appear at the output of the tube 69 as direct current signals and later in the lead as direct current signals of uniform strength and of a length equal to the signals delivered to the band-pass filter 3|.

It was pointed out above that the potential of the condenser 6I is normally adjusted by the potentiometer 62 to the point where the variorepeater is set at mid-gain. If a very weak signal is received, a gain increaser circuit operates to bring up the gain of the vario-repeater in a very short time. This time, for example, may be a minor fraction of a signal length. For a further specific example, this period may be of the order of 5 to 6 milliseconds, so that where the signal length is of the order of 22 milliseconds the time taken to change the gain of the vario-repeater becomes a minor fractionof the signal length.

The signaling current then passes into a transformer 76 through two amplifiers comprising essentially two suppressor-grid pentode tubes il and 18 to a variable loss device 19.' When relay 'lll is in the position shown, the variable loss device 19 is in such condition that the alternating current signal will manifest itself in transformer 80 and thus place an alternating current potential on the terminal of the cold cathode gas-filled tube 8l. This breaks down the gas tube and current flow therethrough is started, .current flowing from a plus battery through the tube Ell, resistance 82 to ground. The drop across resistance 82 causes a second cold cathode gas tube 83 to break down and thus apply positive potential to the condenser SI. Since the impedance in this condenser charging circuit is very low, the condenser 6I is charged rapidly and the gain is changed, for example, in the order of 20 decibels in approximately 5 milliseconds.

When the gain has been brought up to the point where a direct current signal is produced by the tube 69, manifesting itself through the release of relay 10 and the movement of relay 'Il from its spacing to its marking contact, this gain increaser circuit is disabled.

The disabling is done in two steps; ilrst, the armature of relay 'l0 moves from its front cntact and thus opens the circuit of the variable loss device 19 so that this circuit now becomes opaque to alternating current and the alternating current ceases to flow in the transformer i0. Thus the circuit for activating the tube Il is disabled. Secondly, and shortly thereafter, when the armature of relay 10 reaches its back contact, a ground is placed on the lower side of the secondary winding of transformer 80 so that the enabling voltage normally applied to cold cathode tube 8l is reduced.

Heretofore the gain increase disabler of circuits, known as vogads, have been operated directly by relay contacts. An analogy would be the charging circuit for condenser 6| passing through the contacts of relay 10. The transient voltage of this circuit, however, on opening the charging circuit, is so high that the relay con-` tacts cannot be used alone, and hence the gain increaser is disabled in the two-step manner just described, consisting of first disabling the activating circuit, and second in disabling the operating circuit of the gain increaser.

In order to keep the potential on the control condenser 6I from going too high when the gain increaser operates, the condenser 6l is shunted by a diode rectifier 8l. This limits the voltage of the condenser 6I to a predetermined maximum value.

Two leads coming from the lower part of the hybrid coil 65 lead to a transformer 85 to apply voltage to the control gap of a cold cathode gas-lled tube B6. This breaks down the main gap and causes the control condenser 6l to be charged negatively. This circuit constitutes a fast-operate backward-acting gain decreaser. This circuit, for example, will reduce the gain by 20 decibels in a period of 4 milliseconds.

Generally the action of the telegrad is as follows. When a weak signal is received, the gain increaser circuit causes the] cold cathode tubes Qi and 83 to close the circuit for the charging of condenser Gi from a source of positive potential, which acts to rectify the alternating current of the signal transmitted through tubes 'l1 and 18.

As the level of the signal at the hybrid coil reaches a predetermined point, the relay Ill will be released and the gain decreaser circuit will come into operation. Due to certain electrical delays and the mechanical delay in the armature travel time of relay 'l0 the gain increaser is not disabled until the gain has gone slightly above the desired point. The gain decreaser then adjusts the signal with the result that a characteristically enlarged head is given to the intermediate stage signal, that is, the signal as it passes through the hybrid coil 64.

When a strong signal is received the gain decreaser and the gain increase disabler relay 0perate at once subject to the inherent electrical and mechanical delays in the circuit and the gain increaser is disabled almost immediately again with the result that the intermediate stage signal appears to have a characteristically enlarged head.

By increasing the speed of the charging circuits of condenser 6i the enlarged head will be made more prominent and by decreasing such speed the enlarged head may be reduced to a minimum.

When the gain decreaser has brought the potential of condenser 6l down to the proper level, tube 8B will cease to function and the charge on condenser Si will remain constant thereafter except for the slow drift to mid-gain through potentiometer 62.

This is shown graphically in the two theoretical diagrams of Fig. 5 and Fig, 6. Fig. 5 represents a strong signal and Fig. 6 represents a weak signal. Both of these figures show a graph ofan intermediate stage signal as plotted between strength of signal and time. In both cases there is a dotted line a slight distance up on the scale of strength. This represents the noise threshold and the sensitivity of the gain increaser. As the signal reaches the telegrad, the gain increaser begins to operate and the gain increase follows the line which ends in a dot and dash line extending in an almost vertical direction in each figure. Some distance up on the strength of signal scale the gain increasecrosses a dot and dash line marked IOperation of Relays 'I0 and 71. This is the operation' of the gain increase disabler. The operate time of the gain increase disabler, however, allows the gain increase to continue until it reaches another dot and dash line further up on the scale of strength of signal. Above this line will be the operation of the gain decreaser and below this line will be the release of the gain decreaser. The gain decreaser, therefore, begins to operate .strength in all cases.

u, letter Y in la well-known code.

' second and,v fourth places.

ci said variable gaindevice.

at a point somewhat above the operation of the gain increase'disabler and theoretically it would operate in a curve similar in shape to a'dotted line passing through this point, but it must be understood that this dotted line is only an indication of the type of curve followed and is not an indication of the strength of current in this circuit. The net result is the deviation of the actual signal from the gain increase graph. This signal deviated in this manner. reaches a high point and then begins to come down to the line representing the operate and release point of the gain decreaser. At the point A, the gain increase disabler begins to operate.V At point B,

the gain decreaser begins to affect the signal. Between points B and C both the gain increaser and the gain decreaser are operated. At point Cv the gain increaser has entirely ceased to function due to the completion of the operation of the gain increase disabler and from point C and, to point D` the` gain decreaser operates to bring the signal down to the desired level. It

will be noted that the intermediate stage signal is of practically the same shape and of the same It is conceivable that if rapid fading of signals either up or down in f strength is taking' place that further adjustments might be made but the characteristic form of the signals shown in Fig. and Fig. 6

representing a strong signal and Fig. 4 reprei senting a weak signal. These figures have been drawn from oscillograms'derivedfrom actual experience and` represent the transmission of the In each c'ase you have a marking signal in the first,l third and fth places and a spacing signal in the The upper line in each case represents the signal as it entersthe band-pass lter 3|. The middleline represents the intermediate stage signal as `it enters the amplifier-detector through the Atransformer 65 and the lower line represents the signal delivered to the receiving distributor over line 15.

i "of Figs. 3 and 4, are changed first into .uniform strength alternating current signals, represented 5 nals into equal'length uniform strength direct current signals comprising a vario-repeater for changing varying strength alternating current signals into substantially uniform strength alternating current signals, lan ampller-detector for changing saidy substantially uniform strength alternating current signals into direct current signals and means for regulating the length of said direct current signals.

4. In a communication system, means for converting varying strength alternating current signals into equal length uniform strength direct current signals comprising a band-pass filter, a vario-repeater for changing varying strength alternating current signals into substantially uniform strength alternating current signals, an amplliier-detector for changing said substantially uniform strength alternating current signals into direct current signals and means for compensating said direct current signals for change in length occurring in said conversions.

5. In a communication system, means for convertlng varying strength alternating current signals into equal length uniform strength direct current signals comprising a band-pass filter, .a vario-repeater for changing varying strength a1- ternating current signals into substantially uniform strength alternating current signals, saidvario-repeater being controlled by a `fast-actingk gain increaser responsive to said varying strength alternating current signals, a gain increase disabler andl a gain decreaser, an amplifier-detector for changing said substantially uniform strength structed and arranged to adjust the gain oi said by the middle lines of Figs. 3 and 4, and hally into uniform strength direct current signals, as

represented by the bottom lines of Figs.V 3 and 4.

What is claimed is: i l. In a. communication system, a telegrad comprising a variable gain device having a gain increase disabler, an amplifier-detector for operating a signal circuit and means in said signal circuit for operating the gain increase disabler 2f. In acornrnunication system, a signal gain adjusting device, comprising a vario-repreater, a forward-acting gain increaser for said variorepeater, a gain increase disabler, and a backward-'acting gainv decreaser for said variorepeater, anampliler-detector, a signal circuit responsive to signals through said vario-repeater and .said amplifier-detector' and means in said signal circuit for operating said gain increase disabler.'

3. In a communication system, means for converting varying strength alternating current sigvario-repeater to a desired signal strength within l a minor fraction of a signal length for changing said varying 'strength alternating current signals into substantially uniform strength alternating current signals, an amplifier-detector for changing said substantially uniform strength alternatlng current signals into direct current signals, means for adjusting the length of said directeur- 'rent signals-to the length ofsaid varying strength alternating current signals and a gain increase disabler responsive to said direct current signals.

7. In a communication system, means for converting varying strength alternating current sig` nais into equal length uniform strength direct current signals comprising a vario-repeater for changing said varying strength alternating current signals into substantially uniform strength alternating current signals and having gain controlling means for adjusting the delivered substantially uniform strength alternating current signal to ya predetermined value within a minor fraction of the length of said signal, said gain controlling means comprising a fast-acting gain increaser responsive to said varying strength alternating current signals, a gain increase disabler and a gain decreaser, an amplifier-detector lor changing said substantially uniform strength alternating current signals into direct current signals, and means to operate sadgain increase disabler by said direct current signals at rthe end of said minor fraction of the length ci said signal.

8. In ja communication system, means ior con-n verting ivarying strength alternating current sig= nais into equal length uniform strength direct current signals, comprising a band-pass flirter, a vario-repeater for changing said varying strength alternating current signals into substantially uniform strength alternating current signals, said vario-repeater being controlled yby a gain in'a creaser responsive to said varying strength alternating current signals, a gain increase disabler and a gain decreaser all constructed `and arranged to function `yithin a minor fraction of a signal length to adjust the delivered substantially uniform strength alternating current signal to a predetermined value, an ampliiier-detector for changing said delivered signalsto direct current signals, a first relay responsive to said direct current signalsJ a second relay responsive to said first Y relay, a delay circuit for said second relay and a circuit arrangement controlled by said relays for delivering uniform strength direct current signais, equal in length to rthe length of said varying strength alternating current signals.

9. In a communication system, means for converting varying strength alternating current eignals into equal length uniform strength direct current signals comprising a vario-repeater for changing said varying strength alternating curren-t signals into substantially uniform strength alternating current signals, said vario-repeater being controlled by a gain increaser responsive to said varying strength alternating current signals, a gain increase disabler and a gain de- :1

creaser, said gain controlling means being constructed and arranged to adjust the delivered substantially uniform strength alternating current signals to a predetermined value Within a minor fraction of a signal length, an amplifierdetector for changing said delivered signals to direct current signals, a rst relay responsive to said direct current signals, a second relay responsive -to said first relay, -a delay circuit for said second relay constructed and arranged rto cause said second relay to operate a minor fraction of a signal-length after .the operation of said ilrst relay and an output vsignal path controlled by said relays in such manner that said second relay controls the beginning of each signal in said output path yand said iirst relay controls the end of each signal in said output path.

10. In Ia communication system, means for changing dii-ferent strength alternating current signals into direct current signals comprising a band-pass lter and vario-repeater for changing said different strength alternating current signals into intermediate stage signals, said intermediate stage signals being elongated by said band-pass filter, means for changing said elongated inter'- mediate stage signals into direct current signals. and repeating -means for changing said direct current signals into uniform strength signals and for adjusting their length to be equal to the length of said diierent strength alternating current signals.

11. In a communication system the method of changing varying strength alternating current signals into equal length uniform strength direct current signals which consist in changing said varying strength alternating current signals into elongated substantially uniform strength al.. ternating current signals, changing said elongated substantially uniform strength alternating current signals into direct current signals and lll .assenza shortening said direct current signals to a length equal to said varying strength alternating current signals.

i2. 'in a communication system the method of changing varying strength alternating current signals into equal length uniform strength direct current signals which consists in changing said varying strength alternating current signals into alternating current signals having an enlarged head, a substantially uniform strength ior a major portion oi their length and a gradually decreasing and elongated tail, changing said last signals into direct current signals and cutting ori' a portion of said direct current signals corresponding to ti enlarged head of said intermediate c.

i3. In a co', teint-ion system the method of changing varying strength alternating current signals into equal iength uniform strength direct current signals ghi consists in changing said varying strength alternating current signale into intermediate stage alternating current signals each having a body portion of uniform strength, a mini head end portion of steeply rising strength slig o y overshooting the strength of said major body portion and a minor tail end portion of elongated and gradually decreasing strength, changing last signals into direct current signals and cutting oil a portion of the head end of each of said direct current signals corresponding to the elongation of said inter-A mediate stage signals.

ld. In a communication system means for changing varying strength alternating current signals into equal length uniform strength direct current signals comprising a vario-repeater for changing said varying strength alternating current signals into intermediate stage alternating current signals, a fast-acting gain increaser for said vario-repeater, said gain increaser being responsive to said varying strength alternating current signals, a gain decreaser for said vario-repeater, a gain increase disabler responsive to second stage direct current signals whereby said vario-repeater is controlled by said gain controllers to shape said intermediate stage signals to have a major body portion of uniform strength, a minor head end portion of steeply rising strength slightly overshooting the strength of said major body portion and a minor tail end portion of elongated and gradually decreasing strength, an amplier-detector for changing said intermediate stage signals into second stage direct current signals, a pulse chopping circuit for changing said second stage direct current signals into third stage direct current signals and for delaying the start of said third stage Signals by an amount equal to the elongation of said iirst stage signals, whereby said third stage signals are delayed in time after said varying strength alternating current signals.

15. In a communication system, means for changing varying strength alternating current signals into equal length uniform strength direct current signals, comprising a vario-repeater, a gain increaser for said vario-repeater comprising a condenser for controlling the bias of said vario-repeater, a low impedance charging circuit for said condenser and an alternating current path for controlling said charging circuit by said varying strength alternating current signals, a gain increase disabler comprising a crossed coil transmission loss element in said alternating current path and additional means for stopping the charging of said condenser, and a gain decreaser for said vario-repeater, an amplier-detector for changing said Aalternating current signals after passing through said variorepeater into direct current signals, relay means operated by said direct current signals for operating said gain increase disabler, and relay means operated by said direct current signals for delivering direct current signals equal in 'length to said varying strength alternating current signals.

16. In a communication system, means for changing varying strength alternating current signals into equal length uniform strength direct current signals comprising a vario-repeater, a

gain increaser for said vario-repeater comprising a condenser for controlling the bias of said variorepeater, a low impedance charging circuit for said condenser and an alternating current path for controlling said charging circuit by said varying strength alternating current signals, a gain increase disabler comprising a crossed coil transresponsive to signals at the input oi said variorepeater comprising a low impedance condenser charging circuit including a cold cathode gas tube, and an alternating current path activating' circuit for said cold cathode gas tube, a gain increase disabler comprising a variable loss transe mission device in said alternating current path and quenching means for said cold'cathode gas oas 7 tube, an i means for sequentially operating said variable loss transmission device and said quenching means.

18. In a communication system, a vario-repeater, a gain increaser for said vario-repeater responsive to signals at the input oi said variorepeater'comprising a low impedance condenser charging circuit including a cold cathode gas tube and an alternating current path activating circuit for said cold cathode gas tube, a gain increase disabler comprising a variable loss transmission device in said alternating current path and quenching means for said cold cathode gas tube, a direct current relay responsive to the output of said vario-repeater and contact means operated by said relay for iirst operating said variable loss transmission device and second operating said quenching means.

19. In a communication system, means for changing varying strength alternating current signals of the order` of twenty milliseconds in length into equal length uniform strength direct current signals comprising a vario-repeater, having a gain increaser responsive to said varying strength alternating current signals, a gain decreaser and a gain increase dlsabler constructed and arranged to change said varying strength alternating current signals into uniform strength alternating current signals within a period of the order of five milliseconds, an amplifier-detector for changing said uniform strength alternating current signals into direct current signals, relay means responsive to said direct current signals for operating said gain increase disabler and relay means also responsive to said direct lcurrent signals for repeating said direct current signals and for rendering said repeated signals shorter in length by a period of the order of ilve milliseconds.

HAROLD L. BARNEY. URIAH S. BERGER. 'ALFRED E. MELI-IOSE.

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