US 2554886 A
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Description (OCR text may contain errors)
y 1951 c. K. STEDMAN ET AL 2,554,886
SYNCHRONIZING CIRCUIT FOR ELECTRICAL COMMUTATORS Filed June 7, 1947 3 Sheets-Sheet 1 I: l8 l6 GE $%Z$ R o PICK UPS 23 flz I cARRIER 2|\ GENERATOR MASTER [4 RING 7 COUNTER L MODULATOR 26 ID l l %J J I TRANSMITTER I A0. 24 POWER I 1 I 28 I I l COMMUNICATION LINKS I I i I I I I RECEIVER DEMODULATOR 34 I F I 1 FILTER s SEPARATOR 32 I PHASING NET. REGTIFIERS I I TRIGGER LIMITER 4o GENERATOR AMPLIFIER STORAGE RIN E SCAVENGING 42 couNTER CIRCUIT 48 REcoRoERs AGENT y 1951 c. K. STEDMAN ET AL I 2,554,886
SYNCI-IRONIZING CIRCUIT FOR ELECTRICAL COMMUTATORS Filed June 7, 1947 s Sheets-Sheet 2 WAVE FORMS IN MASTER SYNC. EQUIP.
TO OTHER TUBES IN MASTER RING COUNTER TO GATHODE 63| OF LAST TUBE J FIG. 5
g 94 14\ 82 mllf so T NEG. BIAS PLATE SUPPLY l SUPPLY MODULATED CARRIER TO SLAVE RING INVENTORS CECIL K. STEDMAN A-C CARRIER IISEQET 'M IJI IIER SOURCE SOURCE N BY FIG. 2
AGENT SEARC RGQWI y 29, 1951 c. K. STEDMAN ET AL 2,554,886
SYNCHRONIZING CIRCUIT FOR ELECTRICAL COMMUTATORS Filed'June 7, 1947 3 Sheets-Sheet 3 T0 BALANCE TO CATHODE OF RING OF LAST TUBE WAVE FORMS m i T SLAVE SYNC. EQUIP.
1 AAA ran I IIII'I I IWI 'II P""W WWM OUTPUT OF I04 II5 OUTPUT OF M W ACROSS I 36 I I I I I I I I I I -J FIG. 5
PLATE l NEG. BIAS SUPPLY SUPPLY FILTER $PHASING NETWORK CARRIER IN AGENT Patented May 29, 195i UNITE ATES PATNT OFFICE SYNCHRONIZING CIRCUIT FOR ELECTRICAL COMMUTATORS Application June '7, 1947, Serial No. 753,296
The present invention relates broadly to electronic commutators and more specifically to a synchronizing method and means for maintaining synchronization between a master commutator at a transmitting point and a slave commutator at a receiving point. In most methods of multiplexed transmissions of intelligence wherein information from several sub-channels must be transmitted over one common carrier channel it is necessary to use some form of commutating means to rapidly and sequentially select each of the sub-channels and to transmit the intelligence therein over the common carrier channel, devoting a difierent portion of each cycle to each sub-channel for transmission purposes Likewise, at the receiving point slave commutating means must function in synchronism with the transmitting or master commutating means in order to segregate and distribute the original separate sub-channel intelligence signals in the common carrier channel to the respective subchannels in the receiving equipment.
In such a multiplex transmission system some means of insuring synchronism between the master commutating device at the transmitting point and the slave commutating device at the receiving point is necessary. The present invention is concerned with the synchronization of slave electronic commutators with a master commutator, each of which comprises a plurality of electron discharge devices arranged electrically so that the preceding device exercises partial control over the grid circuit of the succeeding device. Since there is usually some form of feedback from the last electron discharge device in the series to the first one in the series to reinitiate the sequence of firing, such a seriesoi electron discharge devices is commonly known as a ring counter and in the case of thyratrons being used as the electron discharge devices, a thyratron ring. At the transmitter in such a system, means are provided which render the electron discharge devices conductive in succession until the last device of the series is rendered conductive, whereupon the cycle repeats itself. As each electron discharge device becomes cnductive, its associated sub-channel is automatically connected through to the common or main carrier channel and at the same time the previous electron discharge device in the series has been rendered non-conductive, thus disconnecting its corresponding sub-channel from the main carrier channel. Provision must be also made in the transmitter for transmitting an appropriate signal to the receiver to cause the slave com- 6 Claims. (Cl. 177-351) mutator to function in a similar manner. Obviously, it is necessary that the cycle always begins in corresponding electron discharge devices in both the transmitter and the receiver, and at the same time. In other words, both phase and time synchronization are necessary.
An object of this invention is to provide means for generating and transmitting synchronizing signals for maintaining one or more slave rings in synchronism with a master commutator ring.
Another object of this invention is to provide receiving equipment for reception and treatment of synchronizing signals for control of a slave ring associated with said receiving equipment.
An additional object of this invention is to provide means for the initiation of the firing sequence in a slave commutator ring in synchonism with the master ring.
A further object of this invention is to provide means .for phase synchronization of the slave ring with the master ring once each cycle.
An additional object of this invention is to provide means for reestablishing synchronization automatically after each interruption of the synchronizing signals.
Another object of this invention is to provide means for time synchronization between the master commutating ring and a slave commutating ring.
A further object of this invention is to provide means for phase synchronization between a master commutator ring and a slave commutator ring.
The above objects and other features of this invention will become apparent to those versed in this art from the following description when studied in conjunction with the drawings herein.
Figure 1 is a block diagram showing schematically the relationship between the various components in the transmitter, and receiver units.
Figure 2 is a simplified schematic diagram of the master synchronizing circuit in the transmitting equipment.
Figure 3 shows the voltage waveforms in the various parts of the transmitting equipment.
Figure 4 shows a simplified schematic diagram of the slave synchronizing circuit in the receiving equipment.
Figure 5 shows the voltage waveforms in the various parts of the receiving equipment.
General description To accomplish phase synchronization, one of the electron discharge devices in the master ring counter is designated as the starting point for the beginning of the cycle. Upon being rendered conductive this electron discharge device is caused to transmit a pulse to the receiving equipment. This pulse is necessary to start the cycle in the corresponding electron discharge device at the receiver. At the transmitter re-cycling of the sequential firing in the master commutator ring goes on continuously. However, in the receiving equipment the slave ring commutator can complete only its cycle which has already been started. At the end of its cycle it will become quiescent and wait for the required pulse from the transmitter before starting a new cycle. In order to start, the slave ring counter is entirely dependent upon the special pulse from the transmitter. After starting, it can complete its cycle independently of signals from the transmitter, but provision is made so that it is subservient to a signal continuously received from the transmitter, thereby keeping it in step as the cycle progresses from beginning to end, hence insuring time synchronization. Thus, by transmitting both continuous and pulse signals, both time and phase synchronism are assured in the receiver, provided the received signals have sufficient amplitude to accomplish their intended purpose.
In Figure 1, a diagrammatic block arrangement is shown embodying the essential electronic units and other means comprising this invention. Substantially sinusoidal alternating voltage from source It is divided and fed into channels l2 and [4. The voltage in channel I2 is fed into the first trigger generator I6 in which it is modified in waveform, first to a sawtoothed wave and later to sharp pulses of voltage of very short-time duration. These short-time voltage pulses are emitted from the first trigger generator through channel is and fed into the master ring commutator or counter 28. These short-time pulses of voltage are all of the same polarity and have a frequency of recurrence equal to the frequency of the voltage source I0. At this point it should be pointed out that the alternating voltage from source I9 is used for timing purposes only and therefore could be replaced by any one of a large variety of rhythmically recurrent voltage waveforms, not excluding direct current pulses. Approximately sine wave voltage is shown in this preferred embodiment of the invention and is employed in the equipment presently in use because of the relative simplicity of generating same. Furthermore, the frequency of the source In may be any small whole number multiple of the frequency desired from the sawtooth wave generator and still maintain accurate control.
The master ring counter consists of a plurality of electron discharge devices equal in number to the number of sub-carrier channels which must share their time on the common carrier channel. In the particular version of this invention now in use, the electron discharge devices constituting the master ring counter or commutator are of the gas-filled type commonly known as thyratrons, and for simplicity they shall be so designated henceforth in this application. To those versed in the art, it will be obvious that with appropriate circuit modifications the hard tube type of electron discharge device could be used in lieu of the thyratron or gas-filled type tube as cited herein. Likewise, the general details of construction of a ring counter or commutator is well known to the art and does not concern this invention. As shown in Figure 1, it is the function of the master ring counter to consecutively and sequentially connect the pickups 23 to the communication carrier channel 28 in order that each of the pickups 23 or sub-carrier channels may for a short portion of time have full control of communication carrier channel 28. Each of the voltage pulses from the first trigger generator and amplifier it upon arriving at the master ring counter 2e causes the next succeeding thyratron in the series to ionize and to quench the preceding thyratron. When the last thyratron in the series ionizes, the first one is conditioned to re-cycle automatically, thus, making the process continuous. One of the tubes in the master counter is selected as the starting point for the cycle and its circuits are therefore adapted to deliver a square wave voltage pulse through channel 26 to the modulator 22. One of these square wave voltage pulses is thus delivered each time the starting tube fires, or in other words, once for each cycle of commutation.
Another portion of the sinusoidal voltage from source I0 is passed through channel 54 into the modulator 22. In said modulator the sinusoidal voltage from source i8 and the square wave pulses from the master ring counter are superimposed or modulated upon the carrier frequency coming from the carrier generator 2|. After modulation, the carrier frequency is emitted at 2 with the side-bands of the alternating voltage from channel I4 and the square wave pulses from channel 26 superimposed upon it.
Although a carrier generator 2| and a modulator 22 has been shown they are not essential to the basic concept involved in this invention. For the particular application in which this invention is now being used it was necessary to use radio as a communication link, hence, the use of the carrier generator and its modulator. To those versed in the art, it will be obvious that this same method of synchronization could be used over wire lines as communication link 24. In such an application, the carrier generator and its modulator could be dispensed with, and the sinusoidal voltage from source I E] and the voltage pulses from channel 25 could be transmitted directly over the wires which in such a case would be communication channel 2 3.
The carrier wave and its side-bands in channel 24 are transmitted to the demodulator 3% located in the receiving equipment. In this demodulator the carrier wave is eliminated and the intelligence in the side-bands gives the original sinusoidal voltage as found in channel is and the square wave voltage pulses similar to those in channel 26. This composite signal is passed through the separator rectifiers 32 and segregated into its components. The sinusoidal alternating voltage is passed into the filter and phasing network 34, and the square wave voltage pulses are passed into the limiter amplifier 48. After passing through the filter and phasing network 34-, the sinusoidal voltage is fed into the second trigger generator 36, thus synchronizing its output of short-time voltage pulses with the output of the first trigger generator l6. These short-time voltage pulses in channel 38 are thus held in synchronism with a similar wave pulse in channel 18 in the transmitter unit. Although in the transmitter unit the short-time voltage pulse in channel 18 will fire the tubes in the ring counter in sequence, such is not the case at the receiver. To start the sequence of firing in the slave ring counter, it is necessary that the first tube in the series receive a special form of signal consisting of .one square wave pulse plus one of the trigger pulses. From the limiter amplifier 40 the square wave pulses are passed into the storage and scavenging circuits 42. After a square wave pulse enters the slave ring counetr 46 by means of the channel 64, the first tube is fired by the first trigger pulse received. As a result, the second tube in the sequence in the slave ring counter is so conditioned that the next short-time voltage pulse in channel 38 will fire it and so the series continues to the end of the sequence. Since the filter and phasing network circuits are adapted to introduce an adjustable phase angle, the first tube in the slave ring counter can be caused to fire at the same time as the first tube in the master ring counter, and from there on the sequence keeps in step by virtue of the time synchronizing effect of the sharp voltage pulses in channels 18 and 38, thus it can be seen that time synchronization is accomplished by the shorttime pulses in channel 38 while the phase synchronization is accomplished by the square wave pulses in channel 44.
If at any time during a cycle of operation of the slave ring counter the synchronizing signals from the transmitter are interrupted, the trigger generator in the receiver will be running free as a relaxation oscillator without control and will continue to fire the slave ring counter tubes to the end of the cycle which has already been started. Therefore to this extent operation of the slave ring counter is not entirely dependent upon receiving signals from the transmitter. However, it is subservient to such signals since the time of firing will be controlled very accurately by the time synchronizing signal if received from the transmitter. Upon the completion of its cycle the slave ring commutator will become quiescent until such time that communication between the transmitter and receiver is re-established and the square wave voltage pulses are again produced in channel 44 to fire the first tube in the sequence in the slave ring commutator. If so desired, the trigger generator in the receiver may be prevented from running free by a slight readjustment of voltages without impairing the over-all performance of the system.
In Figure 1, for purposes of simplicity two communication links have been shown between the transmitting equipment and the receiving equipment. However, with appropriate filters in the receiving equipment to separate the intelligence from the synchronizing signals, the intelligence in channel 28 may be passed into modulator 22, modulated upon the carrier frequency from carrier generator 2!, and sent out over channel 24 to the receiving demodulator 3i]. Appropriate filters following the demodulator 30 could then remove the intelligence signals corresponding to those present in the illustrated channel 28 and deliver them to the slave ring counter for commutation. Such an arrangement is now actually in use, but such a combination of filters does not constitute any portion of this invention, hence, for simplicity the system is shown with the separate communication links in Fig. 1. any number of receivers may be set up with their slave ring counters and recorders 48 to pick up and record signals for some distant transmitter.
Transmitter circuits In the schematic diagram of the transmitter circuit shown in Figure 2, groups of components corresponding to the block units in Figure 1 have been enclosed in dashed lines and assigned corresponding numbers. The alternating current Obviously source I0 is shown feeding its energy through a transformer into the grid element of thyratron via conductor 12. The voltages applied to and the components associated with thyratron 50 may be adjusted below the point of recurrent relaxation oscillations in which case thyratron 50 would then be atrigger tube firing only when it received a positive half wave from the alternating voltage source Ill. However, said voltages and components may also be so adjusted that thyratron 50 will function continuously as a relaxation oscillator, the frequency of which is governed by the frequency of the alternating voltage from source III. In the former case, the thyratron 50 could be regarded as a voltage waveform converter having a sawtoothed output provided it received an imput from the substantially sinusoidal voltage source H]. In the latter case, thyratron could be regarded as a source sawtooth oscillatory power synchronized to the frequency of the voltage supply H] by virtue of its receiving an input voltage from said supply. Returning now to the actual functioning of thyratron 50 and its associated components, the condenser 58 is charged with voltage supplied by the plate supply 65, fed through the resistor 50. Likewise, as condenser 58 is charged, condenser 62 will also be charged through resistor 64 since these last two components are in series with each other and in parallel with condenser 58. As this charging process continues the voltage on the plate element of the thyratron 55 rises to a higher and higher value until the rising sinusoidal voltage applied to the grid element of thyratron 53 makes the grid sufiiciently positive for the instantaneously prevailing plate voltage to ionize the gas in thyratron 55, thus firing same and completing the circuit through to the thyratrons cathode. When thyratron 55 fires, it constitutes practically a short circuit across condenser 53, thereby discharging the condenser to a voltage too low to sustain the ionization within thyratron 59, at which time said ionization extinguishes, thyratron 55 becomes an open circuit once again, and the process of recharging condenser 58 repeats itself for another sawtooth cycle. The sinusoidal waveform input to the grid of thyratron 55 and the synchronized sawtooth waveform output appearing across condenser 58 are both shown in Figure 3 opposite grid 55 and plate 55, respectively. It should be noted that upon firing, thyratron 50 also discharges condenser 62 through resistor 54, thus producing a voltage across the grid to cathode circuit of vacuum tube 52. Since condenser 52 was charged with a considerable portion of the total plate supply voltage from and since'the negative terminal of condenser 62 is connected to the grid element of vacuum tube 52 during the discharge process, vacuum tube 52 is blocked momentarily during the discharge of condenser 52. This momentary blocking of vacuum tube 52 will cause its plate voltage to rise sharply. Consulting Figure 3 again, it will be noted that the sawtooth waveform associated with plate 50 and which appears across condenser 58 is considerably changed by the time it arrives, now designated as grid 52, at the grid element of vacuum tube 52. The circuit comprising the condenser 52 and the resistor 64 has an output which is approximately equal to the differential of the input it receives from condenser 58. Therefore, the sawtooth waveform positive voltage pulses from condenser 58 are converted to the sharp negative voltage pulses shown opposite "grid 52 in Figure 3. Because of phase inversion within the tube 52, these short negative voltage pulses on the grid of said tube result in positive voltage pulses of the same waveform on the plate of said tube, as shown in Figure 3 opposite plate 52. Since thyratron 50 is actuated by the steady output of sinusoidal source It, the sharp voltage pulses constituting the output of vacuum tube 52 are accurately spaced in point of time. Returning now to Figure 2 the two electron discharge devices 50 and 52 and their circuits so far discussed constitute the trigger generator and amplifier I6 enclosed by the dashed line.
The pulse output voltage from the plate of the vacuum tube 52 is fed through condenser 68 and conductor l8 into the common grid circuit of the master ring counter several stages of which are shown within the dashed line and indicated as 23. The master ring counter within the dashed line 25 consists of a plurality of gaseous discharge devices such as thyratrons 53, 54, and 55. Although only three thyratrons have been shown in the master ring counter, for simplicity, any number may be used depending upon the number of sub-carrier channels which must be commutated and fed into the main carrier channel. The thyratron ring commutator is a device well known to the art for accomplishing electronic commutation. However, a brief rsum of its operation will not be out of place at this point even though the ring commutator does not constitute a part of this invention.
In the master ring counter the thyratrons 53, 54 and 55 obtain their grid bias from the negative bias supply 15. The plates of the thyratrons obtain their power through resistor 12 from the plate supply 65. In the quiescent state when none of the thyratrons 53, 54 and 55 are conducting, all cathodes are virtually at ground potential. By virtue of the voltage divider consisting of resistors 35, 82 and I8, and other similar voltage dividers in the other counter stages, the control grids will have some fraction, for example about of the total voltage from the negative bias supply. The plates of tubes 53, 54, 55, etc., are connected in parellel and to the common plate supply conductor 14 and common plate load resistor 12. Because these tubes are normally nonconductive there will be no voltage drop in resistor I2. Hence, the full plate supply voltage will be effective at each plate.
Assume now that a sharp voltage pulse arrives on the grid of thyratron 53 by way of condensers 68 and 15 from the trigge generator and amplifier 3. The effect is to reduce the bias on the grid of thyratron 53 sufficiently to fire the tube. Actually, while this same pulse arrives simultaneously at the grids of all thyratrons and any one of them may fire as a matter of chance, for purposes of this description it will be assumed that thyratron 53 by circuit design or adjustment is made normally most susceptible of all to firing. Upon ionization or firing, the oathode of thyratron 53 rises in potential considerably above round (see cathode 53 Figure 3). This positive voltage on the cathode appears across resistor 18, therefore it subtracts from the normally prevailing negative voltage developed by thi resistor in the voltage divider circuit supplied by the bias supply 75, as described. This reduces the negative bias voltage on the grid of the next thyratron 54 and renders this tube more susceptible to firing by voltage pulse from the trigger generator and amplifier 16 than any of the other remaining thyratrons in the master ring counter. During the conduction period in thyratron 53 the condenser 84 will be charged to a voltage equal to that across resistance 18. When the condenser 84 is thus charged, the terminal connected to the cathode of the first thyratron 53 is positive and that connected to the cathode of thyratron 54 is negative. Condenser 84 thereby acts as a D. C. blocking condenser for the cathode of tube 54 while allowing its grid to follow voltage variations developed at the cathode of tube 53. With the grid of tube 54 positive relative to its cathode, the tube fires on the next positive impulse from tube 52. As it does so, the positive voltage developed at its cathode added to the existing voltage on the charged condenser 84 results in the application of a high reverse voltage to the thyratron 53, extinguishing the latter. The voltage reversing or doubling action gained by using condenser 84 in this manner is aided in extinguishing tube 53 by the effect of increased load current flowing through resistor 72 resulting in a lower available anode potential on tube 53 which is to be met or overcome by the tubes positive cathode voltage. The cathode potential may even rise above anode potential in quenching tube 53. Since ionization starts and stops abruptly and the tubes anode current is relatively constant during conduction, the cathode voltage, relative to ground, is a square wave as shown opposite cathode 53 in Figure 3. Upon establishing conduction in thyratron 54 condenser is charged as was condenser 84 and the control grid bias on tube 55 is reduced as it was in the case of thyratron 54, and in this manner the process just described repeats itself in each stage to the last tube (not shown) in the series, whereupon the over-all cycle is repeated since the last tube in the series preconditions the first thyratron 53 by reducing its grid bias. It should be noted that one terminal of condenser 94 is indicated as being connected to the cathode of the last tube in the series. At the ending of the over-all cycle when thyratron 53, or the first tube in this series, is again fired, a pulse thereby generated and applied through condenser 34 will quench the last tube in the series.
The three conductors 38, 33 and 92 brought out from the cathodes of the thyratrons 53, 54 and 55, respectively, are the conductors used for controlling the circuits or other devices which must be operated in sequence. Another method sometimes used is to place a relay between the cathode and ground in the cathode circuit of each thyratron.
The carrier source 2| is the source of energy used as a carrier for transmission of the time and phase synchronizing pulses and may also be used to transmit the intelligence from each one of the sub-channels. The carrier frequency may be either radio or supersonic. For the particular example of the invention shown in Figure 2, the circuit components shown enclosed in the dashed line 22 constitute the modulator. The electron discharge device 55 is a vacuum tube diode-triode adapted to have the required non-linear characteristics suitable for modulation. Substantially sinusoidal alternating voltage from source In is fed along conductor 54 through resistor [5, condenser ll and into the grid circuit of the electron discharge device 55. Additional alternating voltage is fed into the grid of tube 56 from the carrier source 2! through transformer 69. The resultant is the sum of the two voltages, from source It! and the carrier source 2|, applied to the grid of tube 56. The approximate waveform at this point of the circuit is shown in Figure 3, section 51 of the waveform shown opposite grid 56. By virtue of tube 56 being adjusted for modulation, the waveform on the grid as shown in Figure 3 resultsin a waveform appearing on the plate of tube50 as shown in Figure 3, section 59 shown for plate 56. Such a modulated wave could now be transmitted to the receiver and it would contain enough intelligence to keep the thyratrons in the slave ring counter firing in time with the thyratrons in the master ring counter, however, there would be no means to determine or to maintain the desired phase relation between the two rings. In other words, if the sequence of firing in the receiver or slave ring counter dropped one step behind the master ring counter or if it gained one step, there would be no means for correcting this condition. Therefore, it is necessary to transmit an additional synchronizing pulse of voltage in order to accomplish phase synchronization.
Returning again to thyratron 53, the first in the series in the master ring counter, it will be noted that a conductor 26 is connected directly to the cathode element of said tube. When thyratron 53 is rendered conducting, as mentioned before, the cathode rises to an appreciably high positive voltage very rapidly (see cathode 53 waveform in Figure 3). This results in a voltage pulse being transmitted along conductor 26 through resistor 21, condenser 20 and to the diode plate of vacuum tube 56. As a result of this positive voltage on the diode plate a current fiows between the plate and the cathode of vacuum tube 56, thus causing the cathode to also rise to a higher positive voltage during the pulse period (see cathode 5B Figure 3). Since a rise in positive voltage on the cathode corresponds to-a rise in negative voltage on the grid, the waveform on the grid of vacuum tube 50 will appearat this time similarto section 6I in the Waveform shown for grid 56 in Figure 3. Due to the modulation characteristics of vacuum tube 56 this waveform shown on grid 56 will appear in the plate circuit as shown in section 03 of'the waveform for plate 56 in Figure 3. Such a waveform now contains the original sine wave and the phase synchronizing pulse in its side bands and said modulated wave passes through the transformer 01 and out through conductor 20. It may then be directly radiated or passed through sufficient amplifying means to increase its power before being radiated to the receiving station. It should be noted at this point that the pulse transmitted to the modulator from thyratron 53 occurs only when thyratron 53 is ionized; in other words, once for each cycle of operation of the thyratron ring. With slight modifications obvious to those versed in the art and without departing from the spirit and scope of this specification, the phase synchronizing pulse may be applied to the modulator in the opposite polarity thereby causing an increase in carrier amplitude rather than a decrease. However, the final radio frequency amplifier could not then operate as efficiently as with the arrangement shown, since it would be called upon to function at peak power only during a phase synchronization pulse and at other times only at partial capacity. The circuit herein shown enables the radio transmitter to function normally at peak power. If, however, frequency modulation were used instead of amplitude modulation as in the present equipment,
Receiver circuits In Figure 4, the various components shown enclosed in dashed lines correspond to similarly numbered block units shown in Figure 1. The modulated carrier as received or after being amplified is fed in through transformer I02 to the demodulator 30 which consists of a diode vacuum tube detector I04 and its load resistor I06 and filter condenser I08. The modulator carrier has the waveform shown at the input to I04 in Figure 5. The diode rectifier I04 demodulates the received signal and delivers to its load resistor I06 a voltage having a waveform similar to that shown in Figure 5 for the output of I04, which consists of a small amplitude sine wave with periodic larger amplitude negative pulses. At this point there may still be some carrier present. Therefore, the signal is then passed through the resistance and condenser filter consisting of the condenser H0 and the resistance I09. The voltage appearing across condenser H0 is then fed through condenser II2 into the separator rectifier unit 32 consisting of the diodes H4 and IIS and their associated components. It should be noted at this point that the plate of diode I I4 is connected to the cathode of diode H0. The local circuit of the diode H0 beginning at its plate, which is also connected to the condenser II2, includes the reactor H8. the battery I20, the resistor I22 and the cathode of the same diode H4. The cathode of said diode H4 is also the output terminal and its voltage is delivered through condenser I30 to the filter and phasing network 34. The local circuit of diode II6 starting at its plate element includes the resistance I20, the battery I26, the reactor H8 and the cathode of the same diode H6. The output of the diode H0 is taken from its plate through lead I28. The bias batteries I20 and I26 are each connected in series with their respective diodes with the positive terminal of the battery I20 connected to the plate element of the diode H4, and the negative terminal of the battery I26 connected to the plate element of diode H0. The battery I 20 in series with diode Il4 has its voltage adjusted to be equal to or slightly greater than the peak value of the sinusoidal voltage supplied to the diode H4 from the rectifier circuit including the diode I04. The bias voltage from battery I20 has a limiting function in that with its value adjusted as described the sinusoidal component in the input to diode I I4 corresponding to the sinusoidal voltage from the A. C. source I0 in the transmitter can pass through said diode II4 without change and on through the condenser I 30 to the filter and phasing network 34. However, because of the output of diode I04 coming from its cathode the phase synchronizing pulses from the transmitter are delivered to the plates of diode II as strong negative voltage pulses. Since the negative half cycles of the-sinusoidal components are practically equal to the voltage of battery I 20, cutoff in the diode IIt is approached but not exceeded by the sinusoidal voltage. However, when the strong phase synchronizing negative pulses apforms.
pear at the plate of diode H4 complete cutofi is effected. Hence, these pulses are canceled out by this procedure. Actually the output of diode II4 will not be perfectly sinusoidal for all wave- This characteristic is shown in a fiat portion of the waveform in Figure 5, show as the output of H4, and in time phase with the large amplitude negative pulses in the waveform of the output of I04, same figure.
By reverse process, due to the fact that diode H6 is connected in reverse with respect to diode H4 and battery I26 biases diode H6 beyond cutoff for all signals except strong negative pulses of voltage, the sinusoidal component of the demodulated wave is eliminated in this circuit and only the phase synchronizing pulse component is passed through, being substantially unchanged, as shown in Figure for the output of H6. These pulses of negative voltage are fed through conductor I28 into the limiter amplifier 46 to the grid of vacuum tube I32. A negative pulse on the grid of vacuum tube I32 results in a rise in voltage on the plate of said tube (see output of I32 in Figure 5). The resulting positive pulse passes through condenser I33, through diode I34 and out of the limiter amplifier circuit 40 to the storage and scavenging circuit 42 to charge the storage condenser I36 (see voltage across I36}? Figure 5). Because of the, valve action of diode I34, the positive pulse from the plate of tube I32 after charging condenser I36 cannot leak back and be drained off by resistor I31. As shown in section IE5 of the output of II 4 in Figure 5, the phasing pulse from diode II6 occurs one-half cycle ahead of the peak of the timing wave, therefore it is necessary that condenser I36 store said phasing pulse until the timing wave arrives because it is the sum of the phasing pulse and the timing wave which is necessary to control the firing of the first thyratron in the slave ring 46. The grid to ground circuit of thyratron 43 consists of resistance 4i, conductor 44, resistance I35 and resistance I 38. Since the terminal of condenser I36 connected to the grid end of resistance 535 is positive, the net result is a reduction of the quiescent negative voltage on the grid of thyratron 43 when condenser I36 becomes charged through diode I34. The resulting voltage on condenser I36 produces a reduced bias on the control grid of thyratron 43 which preconditions this tube to be susceptible to firing by the next pulse from the trigger generator and amplifier 36. Upon ignition or ionization of thyratron 43 the counting or commutating cycle in the receiver will have been started and there is no further need for the charge. stored in condenser I36. vThere-- fore, to accomplish the removal of such charge in condenser I36 a lead I41 connected directly to the cathode of thyratron 43 feeds a voltage pulse through resistance I42 to the grid of the vacuum tube I44. Since the cathode of thyratron 43 is positive with respect to ground, this puts a positive voltage on the grid of triode I44, thus, causing the plate to cathode circuit of said triode to discharge the stored voltage in condenser I36 with the firing of the thyratron 43.
The trigger generator and amplifier enclosed by dashed line 36 need not be discussed in detail here since it is preferably identical with the corresponding circuits in the transmitting station.
As cited before, the trigger generator has an output connection to the slave commutator ring 46 through condenser 38 which delivers time synchronizing pulses to the ring counter and con:
tinues to do so even though reception from the transmitter is momentarily interrupted during a cycle of operation. Hence, after the cycle has once been started, the trigger generator can continue to fire the thyratrons in the slave ring 46 to the end of said cycle. As in the case of the transmitter trigger generator, the receiver trigger generator is also subservient to an alternating voltage input derived from the filter and phasing network which has an output waveform substantially corresponding to that of the alternating current power source at the transmitter. The filter and phasing network 34 is necessary to improve the waveform of the output of diode H4 and to provide some phase control of the time synchronizing voltage pulse output of the trigger generator and amplifier 36. Such control is necessary in order that firing of corresponding tubes in the master ring counter and the slave ring counter can be initiated and terminated simultaneously in both rings.
The design and operation of the slave ring commutator in the receiving circuits is practically identical to those same circuits in the transmitter. Therefore, they need not be discussed here in detail. However, one difference does exist and that consists of omitting, in the slave ring, the direct current connection between the cathode of the last thyratron in the sequence and the grid circuit of the first thyratron 43 in the sequence. This omission prevents preconditioning of the grid of thyratron 43 when the last thyratron fires and thereby prevents automatic re-cycling of the slave ring counter, each cycle being initiated only when a phase synchronizing pulse signal has been received and stored in condenser 136. It is, however, necessary to provide the capacitor I56 connected between the cathodes of the first and last tubes in the sequence in order to quench the last tube upon the firing of the first one. It will therefore appear that the commutation cycle once started by the ionization of tube 43 will continue through to the end of the sequence but will stop there and not repeat with firing of tube 43 until reception of the required phase synchronizing pulse and a coincidental timing pulse from tube 36. In this manner, phase synchronization is reestablished at the beginning of each commutation cycle of the slave ring. As in the case of the master commutating ring, the slave ring has leads I46 and I43 in Figure 4) brought out from the thyratron cathodes for controlling the devices or circuits which must be operated in the proper sequence; or in lieu of the above, a relay may be placed in each thyratron cathode lead as previously described.
The above is a preferred embodiment of this invention, and to those versed in the art many variations of same will be immediately suggested by the disclosures herein. Therefore, we (101106 intend to be limited to the specific circuits, components or methods disclosed in the drawings or specification of this application.
1. In a telemetric system, a continuouslyoperable transmitting circuit having a plurality of elements operable successively in recurring cycles to select individual transmitting sub-channels for intelligence transmission, a receiving circuit counter having a plurality of elements, including a starting element and corresponding to said transmitting circuit elements, and associated means to operate them successively through a single complete counter cycle to selectively enersize individual receiver sub-channels corresponding to said transmitting sub-channels, means operable to transmit and receive a time synchronizing wave synchronized with the successive operation of the elements in the transmitting circuit, and further operable to control said associated means to synchronize the receiving circuit counter elements with the transmitting circuit counter elements during each cycle of operation thereof, and means operable in response to each full cycle of operation of said transmitting circuit to transmit and receive a phase synchronizing impulse therewith for application to said receiving circuit counter starting element to initiate operation of said counter in recurring cycles synchronously with said transmitting circuit, thereb to selectively energize said receiver sub-channels synchronously with their corresponding transmitting sub-channels for transfer of intelligence over such sub-channels intermittently.
2. In a telemetric system, a continuously operable transmitting circuit having a plurality of elements operable successively in recurring cycles to select individual transmitting sub-channels for intelligence transmission, receivin circuit counter means having a plurality of counter elements, including a starting element, correspondin to said transmitting circuit counter elements and inherently operable successively through a single complete cycle of the counter to selectivel energize individual receiver sub-channels corresponding to said transmitting sub-channels, means operable to transmit and receive a time synchronizing wave synchronized with the successive operation of the elements in the transmitting circuit, and further operable to synchronize the receiving circuit counter elements therewith during each cycle of operation thereof, and means operable in response to each full cycle of operation of said transmitting circuit to transmit and receive a phase synchronizin impulse therewith for application to said receiving circuit counter starting element, the dura of such synchronizin impulse substarfiifally e ce'difig'and overlapping, in point of time, a synchronizing peak of said time synchronizing wave, and the magnitude of such synchronizing impulse being such that neither of said impulse nor synchronizing peak alone is sufficient to initiate a cycle of operation of said counter, but the resultant of both is adapted so to initiate such operation, whereby said counter is initiated in recurring cycles of operation synchronously with said transmitting circuit, thereby to selectively energize said receiver sub-channels synchronously with their corresponding transmitting sub-channels for transfer of intelligence over such sub-channels intermittently.
3. In a telemetric system, a transmitting circuit counter having a plurality of elements operable to select individual sub-channels successively for intelligence transmission, first wave generating means actuating said counter through recurring cycles of operation of its elements in succession, a receiving circuit including a normally free running wave generating means having means for establishing its normal frequency substantially at that of said first Wave generatin means and also having synchronizing control means therefor responsive to a time synchronizing wave to override said frequency establishing means, a receiving circuit counter having starting control means and having a plurality of elements controlled by said normally free running wave generating means for successive operation corresponding to the sequence of said transmitting circuit counter after such receiving circuit counter is started, such elements in turn controlling energization of receiver sub-channels corresponding to transmitter sub-channels, time-synchronizing means transmittin and receiving a wave synchronized with said transmittin circuit Wave generating means for application to said synchronizing control means of the receiving circuit wave generating means to synchronize operation thereof, hence of said receiving circuit counter, with said transmitting circuit wave generating means and counter, for energizing receiver sub-channels in precise synchronization with corresponding transmitter sub-channels, and phase-synchronizing means transmitting and receiving a synchronizing impulse once each cycle of operation of said transmitting circuit counter for application operatively to said starting control means, to initiate cyclic operation of said receiving circuit counter in phase synchronization therewith, whereupon the receiving circuit counter, after each start, runs through the ensuing cycle of operation of its elements under control of said normally free running wave generating means at times when the time synchronizin wave is received and applied thereto and also at times when it is for any reason interrupted.
4. The telemetric system defined in claim 3, wherein the means for transmitting and receiving the generated wave and the phase synchronizing impulses operate in a single transmission carrier channel, and include means at the transmitter to mix the time synchronizing wave and the phase synchronizing impulses for application to the carrier, means at the receiver to separate such wave and impulses, such separating means comprising a biased detector insensitive to the separated wave but operatively connected to the starting control means to deliver the separated impulses thereto, and an amplitude limiting detector responsive to the separated time synchronizing wave but insensitive to the separated impulses, and connected to the synchronizing control means.
5. The telemetric system defined in claim 4, wherein the starting control means is responsive selectively to the combination of a separated impulse and a concurring cycle of the separated time synchronizing wave, said system further comprising means applying the output of the amplitude limiting detector to the counter starting control means, storage means responsive to the biased detector to store and thereby prolong the separated phase synchronizing impulse produced thereby for application to the starting control means in time coincidence with a cycle of such detector output, and means connected to the receiver counter and operable to discharge such storage means automatically in response to each cycle of operation of such counter.
6. The telemetric system defined in claim 3, wherein the receiving circuit counter elements comprise thyratron switch tubes, cathode load resistors therefor, direct-current connecting means interconnecting the cathode of each tube with the control grid of the succeeding tube cascade fashion, and direct-current blocking condensers interconnecting the cathode of each tube with that of the tube succeeding it, means to apply anode voltage to said tubes through a common plate load resistor, means interconnecting the receiving circuit wave generating means and the control elements of each of said tubes, and. means, including the starting control means, in-
15 16 terconnecting the control element of only one of said tubes with the means receiving the phase UNITED STATES PATENTS synchronizing impulses. Number Name Date CECIL STEDMAN' 1,914,407 Demarest June 20, 1933 HARRY PRICE 5 2,048,081 Riggs July 21, 1936 ROBERT WISNER- 2,055,309 Ramsey Sept. 22, 1936 2,076,335 Dallenbach Apr. 6, 1937 REFERENCES CITED 2,381,920 Miller Aug, 14, 1945 The following references are of record in the 2,400,574 Rea et a1 May 21, 1946 file of this patent: 10