US2806901A - Electronic message timing circuit - Google Patents

Description

Sept 17, 1957 s. K. FERGUSON 2,806,901

ELECTRONIC MESSAGE TIMING CIRCUIT Filed April 2'3, 1953 3 Sheets-Sheet 1 Sept 17, 1957 s. K. FERGUSON ELECTRONIC MESSAGE TIMING CIRCUIT 3 Sheets-SheetI 2 l Filed April 23, 1953 m25 d .me SENSE @ma INVENTOR. I SYRL K. FERGUSON fylLa/-ney4 @23955 imm Sept 175.1957 s. K. FERGUSON ELECTRONIC. MESSAGE IIMING CIRCUIT 3 Sheets-Shea?l 3 Filed April 25, 1953 w w R. I l M m M I -I l l l K. 1 1 L/ ...4. .71. NON ON Wm y @w I "Il D Ol .III o PIII Il M II.. ...Il Il mv m, wmww nl,... ,Ill BN o Sizw. m5 Nm M @Em m m25 om mwfw. 2. mm mm $2.5 m25 m wwm ,N m25 mww um Y B 5%: Nm. om. i: Q NL.. 9 mi mi o. no. O 6E C w w .L L L E IL .lL lIL ...L IL. IL L L. .a IL, IIL ...L .|.L 1L .L L L 11 5 L I1L JL 1L |.L .....L lJL IL I.L L l.L ...L I.L JL lL ...L mmm mm om 2m www.. wom. non om ...om 35u50 um ,+m En E E hm ohm .mwa

2,306,901 Patented Sept. 17, 1957 Etncrnoruc smssnon rui/mso crncmr Syrl K. Ferguson, Springfield, Va., assigner to the United States of America as represented by the Secretary of the Army ser* The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to a pulse generating system, particularly useful in apparatus for transmission of messages over printing telegraph circuits and the like.

More specifically, this invention discloses a means of providing a time period divided into 71/2 units specifically adapted, though not limited, for use in a printing telegraph system using the standard printing Baudet code.

Accordingly, an object of this invention is to provide a timing circuit for pulsing gas tube ring circuits.

A further object of this invention is to provide a circuit for firing a gas tube ring circuit having a large number of tubes.

Another object of this invention is to provide a means for transmitting the time of day and other procedural and identifying information without the use of wiping contacts of an electromechanical switch.

Present day communication centers, to a great extent, utilize printing telegraph as a replacement `and improvement over Morse code transmission. The reasons for this are economy of band width, a printed copy is had at the instant of reception, and retransmission, as in relay Work, is facilitated by automatic regeneration retransmission, and continuous monitoring facilities may be had without the provision of an operator for each circuit to be monitored.

Certain operations performed by the Morse code operator have not been incorporated in the printing telegraph equipment as now in use. The most important function lost in the transition to the printing telegraph system, is that of inserting the time of day each outgoing message is transmitted. The time of day of transmission was formerly applied to the station copy of the transmitted message by the sending operator with his left hand while he trans- C mitted the message with his right hand. More recently, in the use of automatic Morse code transmitters, the message was first converted to perforated tape form and the time of transmission was recorded on the message form as the tape passed through the tape transmitter. The f time of receipt at the receiving end was and still is inserted manually by the receiving operator, not on the message, but on the station record.

The previously employed timing methods were satisfactory because of the slow speed in traffic handling and the small message volume encountered. Today the demand is speed and more speed and channels and more channels; along with these demands is a dire need for automatic message timing device. It is accordingly an object of this invention to fulfill that need.

A prior device which performs certain of the above needs is disclosed in my Patent Number 2,584,997 issued February l2, 1952. The present invention is an improvement thereover particularly in the substitution of an electronic ring switching means and its associated circuits for the commutator contacter as disclosed in the above mentioned patent.

A simplified block diagram of the timing system is shown in Fig. l.

Fig. 2 shows a part of the system including the oscillator, the squaring amplifier, the phase inverter, the cathode follower, the 8 stage distributor, the 6 stage gate, the output amplifier, and the flip-Hop ring driver.

Fig. 3 is a circuit diagram of the 52 stage distributor and relay circuit,

The system disclosed herein begins its cycle of operation at the end of each message transmission at which time a signal or voltage is supplied to demand relay 17. This is merely an oft-on switch which allows the timing circuit to begin the transmission of the time of day and certain other predetermined information.

In order to effect the transmission of the above mentioned information at the end of a transmitted message, this system must be ready to function at all times. Therefore, all voltages are applied and the equipment is in full operation when in a stand-by condition except there is no trigger pulse applied to the ilip tlop character ring driver 18 and the output amplifier relay 7i) shown in Fig. 2 is disabled. During this time the oscillator 11, squaring amplifier 12, phase inverter 13 and one side of the dual cathode follower 14 are operating thereby producing a positive pulse train which fires the eight stages of the 8 stage distributor 15 in sequence. The output of the first six of these stages is fed into one input of the 6 stage gate circuit 16 to be used for sequentially transmitting the coded information applied to the other input of the 6 stage gate circuit from the 52 stage character ring 19. During the stand-by period, there is no input to the gate circuit 16 from the character ring 19 and the output yamplifier relay 70 is disabled, thus preventing any signal from being transmitted.

When the demand relay 17 is energized, the ilip flop character ring driver 18 is triggered thus providing the two cathode follower stages to be alternatively operative for driving the 8 stage distributor 15. A second output from the ilip op character ring driver 18 is used to directly trigger the 52 stage character ring 19. The character ring 19 applies to the second input of the gate circuit 16 the preset information in the form of voltages similar to those obtained from the output of la teletypewriter from the relay circuits 301-352 shown in Fig. 3. Each of said relay circuits stores a code form of a particular letter to be transmitted and this code form of the letter is applied to the 6 stage gate circuit by conductors marked 1, 2, 3, 4, 5. In the lower part of Fig. 2, the corresponding input connections to the 6 stage circuit 16 are shown. This coded form of the preset information is permitted to be selectively transmitted from the gate circuit 16 by the distributor 15 which pulses only one stage at a time.

The variable information relating to the time of day is provided by the one pulse per minute synchronous switch 22 and the time code converter 21. The time code converter 21 changes the time of day into the printing telegraph code and at the same time stores this code until the neXt time pulse is received. The timing element 22 and the time code converter Z1 may be of the type disclosed in my aforementioned Patent Number 2,584,997.

The character ring 19 selects this timing information stored by the time code converter during the course of its cycle and thereby makes available to the gate circuit 16 the coded form representing the time as indicated by numerals. The term character is used throughout this spccication as meaning a number or letter.

The total number of characters referred to in the preceding discussion are not the limits of the invention, but merely the requirements in a particular installation.

Referring to Fig. l, oscillator 11 is provided as a timing element for the unit length pulse of the printing telegraph code and runs at approximately 45 cycles per second at which frequency the period of one sine wave cycle equals 22 milliseconds. This period is used because the accepted standard rate of transmission is 60 words per minute and the average number of characters per word is considered to be live plus a space, thus requiring six characters to be transmitted each second. The time allotted to each character therefore is approximately 165 milliseconds. The Baudot code used herein utilizes six pulses of unit length and one pulse of one and one-half unit length to transmit each character; thus each pulse has a period of 22 milliseconds.

The rst pulse of the Baudot code is the start pulse, the next live pulses `carry the intelligence and the stop pulse comprises a remaining period of approximately one and one-half time units. The standard printing telegraph or Baudot code presently consists of a marking stop pulse of 1.42 units or approximately 31 milliseconds duration. This stop pulse of 1.42 units is merely the minimum since during idle conditions the stop pulse could be extended indefinitely.

In view of the diiculties encountered in precise stopping and starting of an oscillator, it was decided to use a continuously running oscillator. It was also decided to use a stop pulse of 1.5 units duration because of the impossibility of acquiring a 1.42 pulse with a continuously running oscillator or multivibrator. There is no impairment of signal quality and the dierence in duration of a character by only approximately 2 milliseconds is not apparent without precise measurement. Furthermore, the International Standard is to be a 71/2 unit code.

The oscillator 11 provides a sine wave output which is squared by the squaring amplifier 12 whose output is divided into two channels, one going directly to the dual cathode follower 14 and the other channel incorporating a phase inverter or delaying device 13 for delaying the squared signal 180. The two squared signals are diierentiated and applied to grids of the dual cathode follower stage by capacitors 24 and 25 as shown in Fig. 2. The cathode followers 28 and 29 are biased to cut off by potentiometers 26 and 27 so that the negative pulses are discarded.

At the output 35 of the dual cathode follower stage, a train of pulses is provided and if both cathode followers were simultaneously operative, these pulses would be spaced apart 11 milliseconds. However, only one cathode followerV has plate voltage applied at a time, therefore, the pulses are spaced at 22 millisecond intervals so long as relay 34 remains in one position. In such a case these pulses would trigger each stage of the 8 stage distributor 15 at 22 millisecond time intervals and would require 176 milliseconds for each character transmitted; the stop pulse would consume two time units instead of the desired 1.5 time units. This would not comply with the standard rate of 60 words per minute as set forth above, and merely increasing the frequency would shorten the time space between pulses to less than the standard 22 millisecond interval. l

Relay 34, which is part of the ip op character ring driver 1S, is used to switch the plate voltage from one cathode follower stage to the other during the stop pulse period thereby reducing the time between two successive pulses in this one period to 11 milliseconds or 0.5 units. This 11 millisecond pulse plus the rst pulse in the next series added together give the 1.5 unit stop pulse. Since the next seven pulses are also spaced 22 milliseconds apart, the second group of pulses is effectively shifted along the time axis 11 milliseconds with respect to the rst group of pulses as is illustrated in Fig. 1 between blocks 14 and 15.

It follows from the above discussion that there is provided by the timing circuit two series of pulses, the individual pulses being spaced by 22 milliseconds, and a time interval between the series of pulses which is only one-half as great as the spacing between the individualpulses or 11 milliseconds. This cycle of operation continues so Vlong as the equipment is being operated.

Itis obvious that principles of the present invention can be extended to provide a time interval between successive pulse trains that is a third of the time unit between successive pulses in the pulse train by using three channels feeding three `output stages with the second a-nd third channels having 120 and 240 phase delay stages respectively. It follows then that the time interval between successive trains could be made any aliquot part of the time unit between successive pulses in the pulse trains by merely providing the appropriate number of output stages and a separate channel having the proper delay for each output stage.

The output stage does not necessarily need to be a `cathode follower, as any device which will provide the necessary signal strength and the proper output impedance could be used in this system.

The 8 stage distributor 15 comprises 8 gas tubes which are each normally biased beyond cut olf by a bleeder circuit from ground to negative volts at A. When the distributor is iirst turned on triode 36 begins to conduct which causes 4the voltage at point 37 to become a positive 35 volts; the voltage at this point normally is negative. This positive or priming condition is applied to the control grid of stage 1 through resistors 39 and 41 which now places stage l in a condition to become a conductive upon the reception of a positive pulse from the output 35 of the dual cathode follower. It is noted that normally a negative voltage is applied to the control grid by resistor 41 from the bleeder circuit having resistors 38, 39 and 40. This normal bias Which is also applied to the other seven stages of the distributor is suicient to keep each of these seven stages in a non-conductive state regardless of the reception of a positive input pulse which arrives from the dual cathode follower.

When the first pulse is received at the control grid of stage 1 after the positive bias is present, gas tube at stage 1 breaks down and conducts. The voltage at cathode 45 is normally slightly negative due to the negative voltage applied via bleeder circuit 48, 44 and 46. When the tube conducts, this voltage is approximately a plus 35 volts ,and is applied as a conditioning voltage to the control grid of stage 2.

The tube 36 is no longer conducting because the voltage drop across the common plate load resistor 56 for the gas tubes causes tube 36 to become non-conductive and therefore the conditioning voltage is no longer applied to the control grid of stage 1. The absence of this voltage does not affect the conduction of the gas tube during the time it is ionized, but once the tube is extinguished, the negative bias prevents the tube from ring by the mere reception of a positive pulse from the dual cathode follower stage.

When the second pulse is received from the cathode follower, stage 1 of the distributor is conducting, thus providing the positive enabling voltage on the control grid of stage 2. This second pulse causes stage 2 to become conductive. The circuit from the positive voltage of the power supply to ground through stage 2 includes plate resistor 56 and the cathode resistor 49 and capacitor 47. The capacitor 47 is relatively large, being in the range of .O2 afd. thereby preventing an instantaneous rise of the cathode voltage when the tube rst becomes conductive. Since the voltage drop across this type of gas tube (GL 5663) is approximately 15 volts when it is ionized, the voltage on the plates of all the tubes including stage 1 of the distributor is reduced to approximately 15 volts. Stage 1 is thereby extinguished, the cathode voltage, as explained above, being 35 volts.

None of the other stages are fired by the reception of the second pulse because none of the stages have the positive conditioning voltage applied to its control grid.

The third pulse in turn lires stage 3 and extinguishes stage 2. The fourth pulse lires stage 4 and .extinguishes stage 3 and each successive pulse continues in a similar manner. When stage 8 tires, it is clear from the drawing that stage l is again conditiened to be tired by the next pulse.

Tube 36 remains cut o so long as the distributor is running and its only function to start the distributor.

Starting at zero time, cathode follower 28, for example, may have plate voltage applied through contact 30 of relay 34 of the iiip op circuit 18 until a group of seven pulses with 22 millisecond spacing is provided at the common cathode connection 35. Each pulse i'lres a successive stage of the distributor and the output from the cathodes of the first six stages of the distributor is applied to the six stage gate circuit 16 of Fig. 1.

The output of stage 7 is fed into the iiip flop circuit 18 through the demand relay 17 via conductor Sti. This positive pulse is applied to control grids of both tubes 51 and 52 of the nip flop circuit. These tubes may be, though are not necessarily, gas lled since any bi-stable multivibrator could be used. Ir tube 52 is conducting when cathode follower 28 is conducting, the positive pulse from stage 7 Will have no aiect on tube 52, but Will start tube 51 conducting. When tube 51 conducts, the voltage drop across resistor 53 is coupled through capacitor 54 to the plate of tube 52 thereby causing tube 52 to cut off. This in turn causes the relay 34 to become de-energized thereby switching the plate voltage from cathode follower 2S to section 29.

It is apparent from the above that the tiring of stage 7 triggers the flip iiop circuit 18 so that cathode follower 29 begins to function thereby providing the next pulse to stage 8 at a time of only l1 milliseconds after stage 7 is tired and simultaneously extinguishing stage 7. Stage l tires 22 milliseconds after stage 8 is ionized and stage 8 is then extinguished. Since the stop pulse is timed by stages 7 and 8, it will be seen that the stop pulse is 1.5 units or 33 milliseconds in duration. Cathode follower 29 is utilized for the next character to be transmitted by the teletypewriter up to the firing of stage 7 when the original train of pulses is again resorted to. In other words, all odd numbered characters are timed by one stage of the dual cathode follower and all even numbered characters are timed by the other stage.

Thus it is apparent that the timing circuit provided by the oscillator, squaring amplifier, phase inverter and dual cathode is elective for producing pulses timed for e'lcient transmission of teletypewriter signals.

Referring now to Fig. 3, a circuit diagram of the 52 stage character ring 19 of Fig. l is shown. This ring circuit operates in a manner similar to the way the 8 stage distributor ring operates; each succeeding stage res subsequent to the firing of the preceding stage and the preceding stage is extinguished when the succeeding stage is tired.

Each of the stages has in its associated plate circuits relay windings 1491-152 which selectively energize their respective relay contacts 301-352. The relay units are wired in a manner to cause the preselected information relating to identification of the local station and procedural information such as that which moves the carriage to be applied to the 6 stage gate circuit 16 shown in both Figs. l and 2. The contacts of each relay are mechanically connected to move together upon energization of the winding and the presence or absence of the leads from the various contacts of each relay to conductors 379* 374 determine the character to be transmitted when the relay is energized.

For example, in this particular installation when stage 12 of character ring 19 is red, the associated relay winding in the plate lead is energized for approximately 165 milliseconds and the code form of the character to be transmitted is applied to the 6 stage gate circuit for this full period. The code form of this character comprises ve units, each unit being either a mark or a space. The 8 stage distributor completes one entire cycle during this 6 165 millisecond period that the code form representing this character is applied to the gate, thus causing the character representing minutes to be transmitted.

It is therefore seen that the character ring is stepped at a much slower rate than is the 8 stage distributor. The 52 stage character ring is pulsed once for each change of the ip op circuit by contacts 31 and 33 of relay 34 while the 8 stage distributor is pulsed eight times for one change of the flip op circuit. In other words there will e one cycle of the 52 stage character ring for each 52 cycles of the 8 stage distributor.

To tire the 52 stage character ring by pulsing all of the grids as was done in the 8 stage distributor circuit is not practical due to the loading eiect of 52 grid circuits. Therefore, a different means of stepping this large ring is employed. The plates of all the odd numbered stages are bussed together and fed plate voltage by contact 31 on relay 34 ofthe flip op circuit. All even numbered stages and character relays are likewise bussed together and supplied with plate voltage from contact 33 of the same relay.

Each stage of the 52 stage character ring is normally biased by a bleeder between the negative volts and ground in a manner similar to the biasing of the stages in the 8 stage distributor. An input conditioning or priming positive voltage is applied to stage 1 by conductor 2M which causes stage 1 to conduct since the plate voltage is already applied to this tube. This tube conducts for 132 milliseconds while the rst six stages of the 8 stage distributor are tired. When the seventh stage conducts the output pulse triggers the ip op circuit which in turn switches the plate voltage from the odd numbered plate bus 71 to the even numbered plate bus 72.

While stage 1 is conducting, a positive voltage is applied from the cathode 202 of stage 1 to the grid 203 of stage 2, thus conditioning this stage for tiring when the plate voltage is applied. When the plate voltage is switched by relay 34 of Fig. 2, it is applied directly to the plate, there being no plate load resistor. Therefore, no auxiliary positive pulse is required to be applied to the grid 203 to tire the gas tube of stage 2. Only stage 2 can tire when all the even numbered stages have the plate voltage applied because no other stage has the positive priming or conditioning voltage applied to its control grid.

There is no extinguishing problem since the plate voltage of the conducting stage is actually removed when the next stage is pulsed.

It is therefore apparent that this method of triggering a ring circuit permits the use of any desired number of tubes without overloading the driver and eliminates any possibility of erratic tiring of the stages.

What I claim is:

l. A code transmitting apparatus comprising a switching device having two output terminals, one of said terminals being connected to a pulse producing means, a distributor connected to and triggered by said pulse producing means, means for connecting the distributor to supply one input to a gate circuit, a character ring circuit supplying voltages which represent code forms of characters to be transmitted to a second input of said gate circiut whereby a coded signal is transmitted by said gate circuit, and a second of said terminals of said switching device being connected to said character ring circuit whereby the distributor and the character ring circuit are pulsed in synchronism.

2. Apparatus as defined in claim l wherein the pulse producing means produces at least two series of pulses having a predetermined time interval between successive pulses of said series and having a time interval between said series of pulses which is a fractional part of said predetermined time interval.

3. A teletypewriter transmitting apparatus comprising a gate circuit having a plurality of stages and having a first and second input and one output connection, a character ring circuit connected to said first input to supply thereto a series of signals representing a character to be transmitted, each 'one of said signals being applied to a separate one of said stages, means triggering said character ring circuit thereby periodically switching different character signals to said gate circuit to be transmitted, an electrical distributor connected to said second input for causing each signal of said series of signals to be sequentially transmitted to said output connection, means providing triggering voltages to said distributor, a multivibrator switching means triggered by said distributor for providing synchronous timing between said triggering voltages and said triggering means whereby the character ring is triggered when said distributor is at an end of its cycle of operation.

4. A code transmitting apparatus having an input and output terminal comprising a source of two series of pulses having a predetermined time interval between successive pulses of said series; an electrical distributor circuit, means connecting said source of pulses to said distributor circuit; a character ring circuit; triggering means having an input terminal and two output terminals; means connecting one of the output terminals of said triggering means to said source of pulses and the other of the output terminals of the triggering means to said character ring circuit, said triggering means including means for selectively feeding said series of pulses to said character ring circuit; a gate circuit having input connections from said distributor circuit and said character ring circuit, an output connection to the input terminal of said transmitting apparatus; switching means connected between the distributor circuit and the input terminal of said triggering means including connecting means to the input terminal of said code transmitting apparatus, whereby input signals operate said switching means to connect the distributor circuit to said triggering means for the initiation of the transmission of predetermined characters.

5. The apparatus according to claim 4 wherein said character ring circuit includes a plurality of tubes and a plurality of relay means, each of said tubes having an operating coil of one of said relays connected in circuit therewith; each of said relay means including'a plurality of pairs of contacts, and electrical connections between seiected contacts of each relay and said gate circuit in accordance with a predetermined code to provide the elements of the information to be transmitted.

References Cited in the tile of this patent UNITED STATES PATENTS 2,468,462 Rea Apr. 26, 1949 2,521,353 Fitch et al. Sept. 5, 1950 2,557,085 Fisk et al. June 19, 1951 2,644,110 Desch June 30, 1953 2,645,713 Pritchard July 14, 1953 2,646,534 Manley july 21, 1953 2,649,502 Odell Aug. 18, 1953 2,687,451 Slayton Aug. 24, 1954

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