US2239489A - Facsimile apparatus - Google Patents

Description

Patented Apr. 22, 1941 UNITED sTATEsf'PATENT osi-fics FACSIMILE APrAnA'rUs .mm v. n nomi. Foren m11, N. Y., and Home G. Miller, Belleville, N. J., assignors to Radio Inventions, Inc., New York, N Y., a corporation of New York Application December 21, 1938, Serial No. 246,972 Y Claims. (Cl.

The present invention relates to phasing of synchronized moving bodies and in particular to framing of facsimile systems and the like.

One object of the present invention is to provide a phasing or framing method and apparatus vuseful in motor driven systems such asthose em- -be evident from the detailed description of the various figures of the drawing.

There are many systems involving a local oontrolling station and a remote controlled station. In general a facsimile receiving system, for instance, must reproduce signals bearing information in a very precise relation to the transmitter. In order to describe the present invention, it is `proposed to define this relation asbeing made up of a rate of operation called synchronization and a phase of operation called framing. The rate o! operation for instance in a facsimile system employing a long sheet of transmitted and received material will determine hcw received characters are related when compared to the transmitter character relations. The phase of operation will determine how -the characters fall withrespect to the sheet. Whilel there are a number of ways in which the rates of operation of a facsimile transmitter and receiver may be equalized,

one of the simplest is to operate motors driving' the transmitter and receiver scanners from a common power source. In a system so synchronlzed, however, the phase or framing of the receiver will depend upon the instant of turning it on and the time it takes for it to reach synchronlsm. The present invention concerns a novel method and apparatus for phasing or framing a ,systemas described above which is synchronized as to the rate of operation by any one of a number ci means.

, Essentially, the invention comprises transmitting facsimile or other signals to be recorded during a marking interval and transmitting a framseparated out and are applied to a phasing mechanism. The phasing mechanism is rendered operable during the marking interval of the rel ceiving recorder and is operated if framing signais are present during the operable or marking interval. The phasing mechanism in operation may introduce an impedance in series with the power supply of the receiving recorder motor allowing it to slow down. In such a case theA amount by which the motor slows down depends on the duration of the framing signal in the marking interval or the amount 'of slowing may be made up of equal increments by operating the motor circuit switch in such a manner that each' time it is opened it stays vopen a predetermined llength of time. The process described above the invention.

Fig. 2 shows a schematic diagram of portions of a facsimile receiver embodying one form of the invention.

The transmitter as shown in Fig. 1 comprises marking signal generating 'means of conventional ing signal during a non-marking interval. At

the receiver the marking signals are applied toa design which may consist in a source of sub-carrior-signal I coupled to a pick-up photo-electric cell l and a balance network I-l by means of the transformer 2-3-4. Photo-electric cell i is contained in the pick-up scanner It. The sub-carrier voltage modulated by thephoto-electric cell is applied acrossigrid resistor 8 to an amplifier tube l having a grid Il, plate Il, and cathode i2. Cathode I2 may receive bias from cathode resistor I3 by-passed by condenser i4, and plate il may be loaded by resistor I5 and energized from any convenient source of plate voltage +B. The amplified modulated sub-carrier signal output from tube l appearing across plate load resistor Il is fed to a resistor I4 thru blocking condenser II. The voltage across resistor 2l is placed on grid 2O of -ampliner tube 28 which also has cathode 3l and plate I3. Cathode 3l receives bias from resistor Il by-passed by condenser I2 and plate Il feeds further ampliners,` carrier modulators. etc. u comprising the transmitter feeding antenna A. In the case of a wireline 34 may be any coupling system suitable to the particular type of line.

'I'his invention as far as the transmitter. is conmarking member and the framing signals are cerned comprises means for introducing a phasimpulses.

tion i8 of cam I8-i9- which closes contact 22 thereby feeding modiulated sub-carrier signals from resistor 24 to resistor 26 and from there to the transmitter 34, causing marking signals to be emitted. During the remainder of the scanning cycle or non-marking interval the larger radius l portion I8 of cam I8-I9 opens switch contact 22 removing marking signals from the transmitter, and closes contact-23, placing phasing sig..

nais from source 21 on the transmitter. The frey quency oi' source 21 is made suiciently different from the frequency of sub-carrier li that thetwo signals and the modulations oicarrier I may be differentiated on a frequency basis in the receiver.

,Thus, the transmitted signal is made up of marking signals and framing signals, although there may also be short intervals of `zero signal between each switch-over while switch --2I--22-23 is in a neutral position. This interval may be con- -trolled by varying the slope of the cam surface between the smaller radius I8 and the larger radius i8, and by varying the space between contacts 22 and 23.

The receiver as shown in Fig. 2 comprises a conventional facsimile receiver 35 attached to antenna A. After amplication and detection the received signals consist of marking signal ,modulations of the rst sub-carrier, intervals of no signal and the phasing signal sub-carrier This composite signal is applied to a separator circuit comprising tuned trap circuits 38--31 and SMQ. Trap 3 8-31 is tuned to the marking signal sub-carrier and the marking signals thereby established across it are applied to the receiver scanner I2. at points III-4i where mally held open to close contact Il by spring 15. Contact $8 is placed across animpedance comprising condenser 1I shunted by resistor 12 in series with the scanner motor 60 and its power supply leads 13-14. Cndenser 1| and resistor 12 are so chosen that when contact 68 is opened as `described above, motor 60 slows down. 'I'he rate at which it slows down may be controlled over a range by the choice of condenser 1I and resistor 12. Thus, if phasing signals are received at the receiver during the marking interval, the driving motor Sil' is slowed down Motor t@ may be a synchronous motor operated from the same alternating current power source, as the'transmitter or other synchronizing systems may be used to maintain rate synchronism as defined above. It will be seen that when in frame no mark will be produced on the back stroke, since the framing signal is not passed by trap circuit td--BL As described, the receiver motor 60 is slowed down during each cycle of scanning by an amount which depends upon the amount by which the re- Y ceiver scanner is out of phase with the transit may be lfurther amplified and rectified and utilized to energize or operate a recording electrode or other mechanism. Trap circuit 38-3@ is tuned to thephasingsignal sub-carrier frequency and voltages appearing across it are applied to' grid i4 of amplifier tube Qt also having a plate t6 and a cathode dii connected to bias resistor 38 by-passedv by condenserel. The plate t8 feeds relay coil its and is. energized from any suitable voltage source at +B. Thus, phasing signals operate the relay associated with coil il@ comprising a core 50, armature 5l, `return spring 52, contact 5l and stop 54. Recorder 42 is run by motor BI) from shaft 6|. A counter-shaft 59 is provided which revolvesvcam 51--58 once for each scanning cycle as was the case' of cam I8- IS. Cam 51-58 moves contact 55 into and out of operating position thru roller S6. When roller 5t ison the smaller radius 5t as shown, contact 5t cannot be closed by phasing signals. but when roller 5t is on` the larger radius El, contact .EE may be closed by phasing signals. Thus, if phasing signals are received during the marking stroke of the receiver, that is while roller 66 is on largerradius 51, contact will close with arm 5I and a. circuit will be completed from wire 53 to wire 66 thru relay coil 65. Wires S3 and $4 are connected to a source of electrical energy suitable for energizing coil to open contact il oi' relay 8548-41-82.

mitter scanner. When the twoare in phase, there will be no further action of the phasing system as long as synchronism is maintained uninterrupted.

Cams I8 and '51 have been shown cut for equal recording and non-recording intervals for each with small, no signal intervals provided for between marking and framing signals. `In many cases it is desirable for efciency of operation to mark for more than half the time and to transmit framing signals during only a small time interval, say for 15 percent of each scanning cycle. This may easily be accomplished by making the larger diameter of cam' it 54 degrees to transmit framing signals for i5 mrcent of each cam revolution and the smaller diameter portion Fit of the cam at the receiver likewise 54 degrees so that the phasing system is operable for 306 degrees, or the marking portion of each scanning cycle. l im 1 A variation of the mode of operation described may be accomplished by delaying the closing of contact t once it is opened by means of a slow return plunger it operating in a dashpot t9. If imance iis made to have only a small eiiect on the speed of motor it@ and the slow return mechanism ci contact @t is made to have a long period compared to half a line scanning Armature 61 is nor- 75 cycle, the phasing will be accomplished by equalincrernents no matter how much or little the phasing is out, until perfect phasing is accomplishefd, or phasing increments may depend upon the amount by which phasing signals overlap thev marking intervals when phasing is out by a large amount, and these increments may decrease as phasing is corrected to a limiting increment determined by the time of operation of the dashpot or a similar time delay device. If idle periods between the phasing and marking signalsA are provided, as described above, the phase relation will be corrected to be nearly perfect, `but may be out by the amount ci these idle periods. lThe idle periods may correspond tc a margin in the received material, so that a quieter but less accurate phasing may be accomplished only at the expense oi margin space. With increased marking time, the equal increments of phase correction become increasingly important.

One outstanding advantage of this present framing system is that once the system is framed, interference cannot, aect" the framing during a part of each lcycle. During the/remainder of the lMamas cycle, onlyinteriklerencel having strong com-` for instance, amplitude selection, may be used to separate marking and framing signals. Again framing signals may-be transmitted for all or only a part of non-marking intervals. Short impulses of framing signals may be utilized in which case equal-increments of framing may be utilized tofull advantage by proper choice of timeiof operation of dash pot 68-10.

, vals, andmeans for shifting the phase. of said. motor by an amount proportional to the duration In Figs. 1 and 2 the letter G represents ground points or common. points'as is electrical circuit representations.

' While one embodiment, with a, few modifications, has been shown vention embraces these and other modifications as will be evident to .those as set forth in the appended claims.

What is claimed is:

1;'In a facsimile system, the combination of, a facsimile receiver, a facsimile recorder, a synconventionalin chr'onized motor for'operating said recorder, in-

dependent means responsive to signals comprising two distinct groups of frequencies, means for dividing receiving' periods into recording and' Anon-recording intervals, means for slowing said motor in accordance' withnone of said groups of frequencies when received during said recording intervals and means for equalizing the slowing of said motor regardless of the duration 0f reception of said last groups of frequencies during said recording intervals. Y

2. In afacsimile receiving system, the combination of, a recorder, a synchronized motor forl driving said recorder, means for dividing re-` ceiving periods into recording and non-recording intervals, means forreceiving marking and phasing signals comprising two distinct groups of frequencies, means for separating said two groups and described, the .in-

skilled in the art,

' for driving said recorder,

vals, and means for changing the phase of said motor in response to said presence. v 3. In a facsimile receiving system, the combination of, a recorder, a synchronized motor for driving said recorder, means for dividing re' ceiving periods into recording and non-recording intervals, means for receiving marking and phasing signals comprising two distinct groups of frequencies, means for separating said two groups of frequencies, means for detecting the presence of phasing signalsduring said recording interof said phasing signals present during said recording interval.

4. In a facsimile receiving system, the combination of, a recorder',v synchronized driving means for said recorder, means for dividing re-` ceiving periods into recording, non-recording and margin intervals, mea-ns for receiving frequency distinctive marking and phasing signals, and means for phasing said driving means in response to phasing signals'received during said recording intervals whereby said marking signals are recorded during said recording intervals plus said margin intervals.

5. In a facsimile receiving system, the combination of. a recorder, a synchronized motor means for dividing receiving periods into recording and non-recording intervals, means for receiving marking and phasing signals comprising two distinct groups of frequenciearmeans for separating said two groups of frequencies, means for detecting the presence of phasingsignals during said recording intervals, means for changing the phase of said motor in response to said presence, and means forv controlling the amount of phase change to be produced relative to the durati l of said phasing signals during said recording intervals.V

JOHN V. L. HOGAN. HORACE G. MILLER..

of frequencies, means for detecting-the presence of phasing signals during said recording inter-

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