US2252380A - Telegraph signal regenerator - Google Patents

Description

Aug. 12, 1941.. KAHN' 2,252,380

TELEGRAPH SIGNAL REGENERATOR' Filed Feb. 2,9, mo 2 Sheets-Sheet 2 [MARK/N6 PEAK 4a RECT/F/ED m2 em +8 l9 wscunnass 1 I149. 4b mvoas VOLTAGE 01 15 33 3/ J I 0 L33J B 32 8DISCHARGE$ 4L ANODE 11H VOLTAGE- 0P5 v 0 v I LOCK/N6 cmcu/r ac. our ur FULL WAVE 'l-IALF WAVE REC'T/F/CATION RECTIFIER 24 Du: r0 RECT/F/ER4 90.6'H/F7' RESULT/INT RECTIFIER vozmas {ACROSS RESISTOR 27,

PEA/(5 OCCUR A THALF FREQUENCY RATE 1 INVENTOR. ALFR 0 KAHN ATTORNEY.

Patented Aug. 12, 1941 Alfred Kuhn, Hollis, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application February 29, 1940, Serial No. 321,398

' 8 Claims. (cl. I'm-69.5)

This invention relates to a telegraph signal regenerator and more particularly to an electronic system for regenerating synchronous signals which may havebeen deformed in traveling through the conducting medium from the transmitter to the receiver.

It is an object of my invention to provide a regenerator which is simple in construction, easy to maintain, and which requires a minimum number oi parts.

it is a more specific object of my invention to provide a regenerator which eliminates, insofar as possible, mechanical commutation means, and which provides dependable regeneration of the received telegraph signals.

It is a still further object of my invention to provide a regenerator which depends for its oporation upon properly timed locally generated impulses, these impulses being coordinated with the received signals for controlling a so-called' .lociciug circuit oi conventional type.

In carrying out my invention I provide means dependent upon the normal rate of reception of the signalling elements for controlling a multivibrator. The output irequency of this multivibrator is held in synchronism by means well i-mown in the art. Such means may, for example. be of the type shown and described in an application Serial No. 169,365, tiled October 16,1937, by Richard E. Mathes, and assigned to the assignee of the instant application. Mathes showed a synchronous corrector applicable to a receiving distributor for a multiplex system. Such a corrector may be employed for maintaining the frequency and phase of my multivibrator suitably coordinated withthe mean frequency of reception of marking signal peaks. However, other means of control oi the multivibrator irequency may be adopted, whether mechanical or electromechanical in structure, provided a source of substantially constant frequency impulses is made available. This multivibrator is employed in combination with rectified pulses representing marking elements of the telegraph signals so as to regenerate signals of substantially squarewave formation, as is done when a. conventional Figure 1 shows diagrammatically a preferred circuit arrangement for carrying out the invention;

Fig.2 shows a typical wave shape representing the unfiltered output'irom a rectifier which in turn is controlled by a multivibrator;

Fig. 3 shows the wave shape oi output energy from an amplifier stage following the rectifier whose output is as shown in Fig. 2;

Figs. to, db, 4c and 4d show respectively ditierent time graphs oi signals and voltages appearing across diilerent portions of the circuit arrangement:

Fig. 5 shows a detail oilmeans for utilizing a i multivibrator whose frequency is equal to twice that of the signal frequency; and,

Figs. t and 7 show time graphs oi resultant impulses obtained by the use oi the means shown in Fig. 5.

Referring first to Fig. 1, I show a muitivibrator Mi? having an input circuit connected thereto which synchronizes its operation in dependence upon a phase cox-rector unit PC, the latter being operative in dependence upon the arrival moments oi the signals. The output from the multivibrator is substantially sine wave in formatlen and is fed across a transformer l to the input circuit of an amplifier tube 2. The output from this amplifier is fed across a transiormer t to a circuit which includes a full wave rectifier 4 and a load resistor 21. Thecathode or th r tifier. 4 is grounded and its anodes are connected to the terminals of the secondary on the transformer II. This secondary has a midtap connected to one terminal of resistor 21,

the other'terminal of which is connected to the grounded cathode.

An electron discharge tube 5 has a control grid connected to the mid-tap on the secondary of transformer 3. This tube is, therefore, controlled by the rectified voltage developed across resistor 21. The output from the tube 5 is utilized in a half wave rectifier tube 8 having in shunt therewith a resistor I of high ohmic value.

The unfiltered output from the rectifier 4 produces a wave shape as shown in Fig. 2. The tube locking circuit is properly controlled. An important'feature of my invention, therefore consists in the provision of a circuit arrangement whereby the incoming signals and the oscillator are caused to cooperate to control the locking circuit.

My invention will now be described in more detail, reference being made to the accompanying drawings in which I is held at cut-oil by the average negative bias produced by the rectifier l and passes current only when the sharp bias peaks approach zero.

The anode voltage excursions or the tube I are shown in Fig. 3.

The purpose of the resistor I is to permit a slow charge to be accumulated on the capacitor 8 during moments of peak voltage oi the'anode in tube 5. The tube 8, being conductive in one direction only, functions when tube 6 becomes conductive to permit the condenser 8 to discharge rapidly. I

The locking circuit is shown within a rectangular broken line encl and comprises discharge tubes 26 and 2! in combination with a number of resistive circuits interconnecting the electrodes and the power supply source. The output leads from the locking circuit aredesignated L and may be considered as feeding to a recorder unit or to keying means for retransmit acoasao signal. In case the spacing signal is prolonged beyond the next instant of zero voltage drop across resistor Zl, the action of condenser it will predominate over that of condenser 8, so

bias on the grid of tube iii to approach zero,

output from the tube ii is led across the primary of a transformer is whose secondary has terminals connecting rvely with the anodes of a full wave rectifier is. secondary isalso provided with a mid- -tap' connecting with one terminal of a load resistor iii and with the control grid in an amplifier tube is. The cathode of the rectifier it is connected to a junction lead between resistors it and 27 so as to efiectively place the circuits of rectifier-s i and is in series.

A keyed tone signal is culled to transformers Iii and i2 and appears as a rectified signal voltage acrossresistor l6. condenser it so as to smooth out the ripple com= ponent appearing in the rectified signal. A suit able bias voltage is thereby obtained for controlling the grid oi amplifier tube iii.

The output from tube is is utilized in the some manner as the output from tube b, but for the purpose oi operating the inciting circuit in the reverse direction. "ihis is accomplished by means of a half wave rectifier tube. to in aht with which is disposed a resistor ll of high c value. The anode of the rectifier it is connected to one side of the condenser. is, the other side of which is connected tothc grid of tube it in the locking circuit.

0n receptlonoi' the marking signal peaks, the rectified voltage across resistor it is a maximum and biases the tube to to cut oii. The voltage on the cathode of rectifier it floats between ground potential and the negative potential derived from the rectifier .t, the latter heingprevalent most of the time and the former during the brief intervals of current interruption across resistor ll. During these briei intervals the grid bias in tube l5 becomes slightly 1 negative than at other times. but not sufiicienily so for efiectinr; any control of tube 2! in the locking unit;

On reception oi. a spacing signal simultaneously with the arrival of a zero-voltage peek at the top end of resistor 2?, tube it draws suiiicient current to enable condenser it to discharge substantially fully. This action results in blocs tube II at the negative wave crest oi a spacing T" resistor is shted W a that tube 2| will remain blocked until the arrival of succeeding marking signal. Thus, as shown in Fig. 4b, the anode voltage of tube It dips slightly as at 80, and only once at the crest of a short marmngsignal on (Fig. do), but dips repeatedly as at 3| during a prolonged marking signal 1212. Here the periodic dips 32 of anode voltage in tube 5 (Fig. 4c) are permitted to maintain control'. Furthermore, during shortspace intervals 81 and long space intervals So the anode voltage oi tube l5 dips to its lowest value and blocking control of tube 2! is likewise maintained. The locking circuit will, therefore, be tripped by the simultaneous occurrence of a spacing signal peak and an impulse from the multivibrator MV. The action oi the rectifier i6 and shunt resistor H is identical with that of rectifier 6 and shunt resistor l, except that they follow the control of the spacing signals, whereas the periodicity-of the latter is constant.

It will be seen from the above description that the tube it is either unblocked slightly by impulses from the rectifier it as when marking signals occur, or is unblocked fully in the presence of spacing signals plus an impulse from the rectifler i, in which case the rectified current across the tube I8 is of suficient mplltude to fully discharge the condenser is and thereby to bias the tube 2| to cut-ofl. This-simultaneous application ci' pulses from rectiflers 4 and it is in excess of the discharge efiect across rectifier E alone and, therefore, the tube ill is controlled predominantly over the control of tube 25. In other words, the sheet of the impulses from the multivibrator is switched to control tube to for biasing the same to cut-ofi upon reception oil a marmng signal and is switched to control tube 25 upon reception of a spacing signal. The time oi occurrence of the pulses is held to the center of each baud by means of the correction unit PC so as to pass the signal to the locking circuit during its best portion.

A typical time graph of a received signal representing dots and dashes and somewhat dismrted from the original square-wove form is Til shown in to. Figs. 4b, 4c and 4d are time graphs drawn to the same time scale as Pic. to. In Fig. 4b the anode voltage of tube iii is shown. The deep depressions occur during spacinu intervals and represent times when tubes [8 and it are conductive. Tube it is only slightly urn-blocked at peaks of the marking signal.

Fig. to shows voltage changes on the anode of tube 5 which result from the operation oi the multivibrator MN. The voltage is high for the greater of the time because the rectifier i biases tube it substantially to cut-oil. Momentorlly, however, the output from rectifier t" is substantially reduced to zero and the bias on the grid of tubeb rises to substantially zero, thus permitting the condenser 8 to discharge quickly across rectifier and the space path of the tube t. It is during these discharge intervals of condenser c that tube to in; the locking circuit is biased to cut-0d.

Fig. 4d shows the regenerated signal having a square wave formation. This is the signal which is delivered by the locking circuit at the output terminals 0L.

Referring now to Fig. 5, I show a detail of an arrangement wherein the control frequency from the mammal minimise even though it possessestwice the -frequencyfotthe signal ire!- rectifier 'l'is also the same as shown in Fig. i,

aasasso of a" train of received signals, means for continuously correcting the phase or said generator quencyl Bu'ch'an arrangement has certain pracwith respectto the marking wave peaks of said signals, a full-wave rectifier receptive of energy from said generator, a second full-wave rectifier receptive of tone frequency currents representing marking signals, two series-connected load re- ,slstors, each appropriately disposed in circuit but is supplemented by a half-wave rectifier 24.

The phase of the voltage delivered to rectifier 24 is'in aquadrature relationto the phase of the voltages delivered to the full wave rectifier I. This is brought about by the use-oi a conventional system of capacitor}? and resistor R in series with oneanother, the interconnection between them being also connected to the anode of the rectifier 24. The cathodes of the rectifiers l and rare interconnected and lead to thegrounded end oi! resistor 21. The other end of resistor 21 is connected with the mid-tap on the secondaryfo! transformer i, the same as shown inFig.l. 4

By means of the arrangement shown in Fig. 5 certain voltages are delivered across. resistor 21 as shown in Fig. 8. The combined rectifiervoltage, however, is shown in Fig. 7. It will be noted that the sharp peaks of no voltage appear only at every other cycle of the multivibrator frequency, intervening voltage dips being counteracted by the output from the half-wave rectiher 24. It is only the negative peaks which represent substantially no voltage across resistor of that type has been disclosed by a. a. Shenk in his application Serial No. 326,902, filed March 30, 1940. It will also be understood by those skilled in the art that various modifications or the invention may be adopted without departing from the soiritfand scope of the invention as defined by the claims to follow.

I claim:

1. In atelegraph signal reseneramr, a lock ing circuit for keyingflthe marking impulses of a signal train. a multivibrator capable of enerating self-sustained oscillations subject to phase correction by a train of received signals. means responsive to the operation of said multivibrator for timing the shifts of said locking circuit from one to another state of electrical stability, means operative during reception of. the wave peak. of a marking signal of baud unit length for producing one of saidshiits in one sense, means operative during the reception at a wave valley representing a spacing B InaI oi' baud unit length for producing one of said shifts in the opposite sense, and means inherent in the cooperative" with a respective one of said rectifiers. and means comprising two capacitive circuits forproducing shifts in opposite senses of electrical stability of said locking circuit, each 'of said capacitive circuits including means for slowly storing a charge when an associated one of said lead resistors draws current, and for suddenlydissipat- 'ing said charge when that resistor ceases to draw current. I

3. The combination, according to claim 2, in which the stated means in each of said capacitive circuits is constituted by a half wave rectifier shunted by a resistor. I

- 4. The method of controlling a locking circuit for the purpose of regenerating telegraph signals received at a substantially fixed baud frequency, which comprises generating a sine wave, continuously correcting thephase of said wave in accordance with said received signals, separately rectifying the energies of said wave and of the marking elements of said signals, slowly accumulating' a capacitive charge during each moment Of rectification or the sine wave energy, slowly accumulating another capacitive charge during reception of each marking signal element, periodically and .suddenly dissipatingthe first mentioned charge at said-baud frequency, suddenly dissipating the second mentioned charge simultaneously with the first whenever thereception of a spacing signal is coincident, causing said locking circuit to shift from a first to a second state of electrical stability in response to the dissipation of the first mentioned charge only,

and causing said locking circuit to shift in an opposite sense in response to the simultaneous dissipation of both said charges.

5. A telegraph signal regenerator comprising a locking circuit having two discharge tubes,

the-electrodes of which are resistively interconnected in such manner that one isnormally blocked while the other draws current and the action of the aforesaid means for continuing the state of electrical stability to which said locking circuit is shifted during the prolongation of. markingandspacingsignalsbeyondanintervalof band unit length.

2. In a-telegraph signal regencrator, a locking circuit for keying the marking impulses of a signal train, an oscillation generator having a substantialiy-sine-wave output at a irequency' blocking of each tube by an extraneous negative impulse causes the other tube to become conductive, each tube having a blocking bias circuit connected between its cathode and control grid, each said control grid being coupled through an appropriate storage capacitor to a suitable COD! trol circuit, a source of periodic impulses delivered at a baud-frequency rate corresponding to the speed of reception of a train of telegraph signals, a full-wave rectifier responsive to said impulses, a second full-wave rectifier responsive to received tone frequency energy representing marking elements of said signals, two inverter tubes, each under the respective control of one of said rectifiers, and means in each of said control circuits for eii'ecting a slow charge and a rapid discharge of its appropriate storage 'capacitor in response to theblocking and unblocking respectively 01' an appropriate once! said slsnal'and to cause the second capacitor to dis.-

charge more effectively than the first during reception-of aspacing signal.

time; approximating the baud unit periodicity is c. In a telegraph signal regenerator a locking circuit rtr re-shaping the marking impulses or aslgnaltraimsaidmarkingimpulsesbeingof normal length equal to a buud' and multiples thereof, and being separated by spacing intervals locking circuit from one to another state of electrical stability, means responsive tothe reception of signals to be re-shaped for correcting the phase of said oscillator, means under control of aesaseo hair to be re-shaped for correcting the phase of said oscillator, means under control of said oscillator for producing short sharp impulses of baudfrequency, and means under the joint control of thereceivedsignalsandofthelastsaidmeans for fixing the moments when the electrical staself-sustained oscillations subjectto p a corsaid oscillator for producing short sharp impulses of baud-frequency; and means under the Joint control of the received'signals and of the last said means for fixing the moments when theelectrical stability of said locking circuit is ing a normal frequency equal to the baud frequency for timing the shifts of said locking circuit from one to another state'of electrical stability, means responsive to the reception-of slarection by a train of received signals, means re sponsive to the operation-of said oscillator for, timing the shifts of said locking circuit from one to another state of electrical stability, means operative during reception of the wave peak of a marking signal of baud unit length for producing one of said shifts in one sense, means operative during the reception of a wave valley representing a spacing signal of baud unit length for producing one of said shifts in the opposite sense, and means inherent in the cooperative action of the aforesaid means for continuing the state of electrical stability to which said locking circuit is shifted during the prolongation of marking and spacing signals beyond an interval of baud unit length.

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