US2257918A - Facsimile apparatus - Google Patents

Description

Oct. 7, 1941. H. c. REssLER FAC'SIMILE APPARATUS Filed Deo. 9, 1938 ||||5||| LFI Il..

Patented Oct. 7 1941 FACSIIVIILE APPARATUS v Hugh C. Ressler, Richmond, Staten Island, N. Y., assignor to Radio Inventions, Inc., New York, N. Y., a corporation of New York Application December 9,193s,seria1No.z44,7`56

5 Claims.

The present invention relates to phasing systems and particularly to framing in motor driven facsimile systems and the like.

One object of the presentI invention is to provide a framing orphasing system particularly adapted to motor driven facsimile systems and the like which is substantially unaffected by ordinary static or similar disturbances.

A further object is to provide a framing system which operates only at the start of program reception` and then remains inactive as long as synchronism is maintained.

Still another object is to provide a framing system in which the number of moving parts is minimized especially during periods of operation while the receiving system is in frame.

Another object is to provide a. framing system which operates independently of the synchronizing system but which utilizes synchronizing signals in its operation.

A still further object is to provide a framing system which operates equally well and without change or adjustment whether the system is synchronized from transmitted signals or from the local power line.

And still another object is to provide a framing system which is simple and which still frames as accurately as is inherently possible in the types of system to which it may be applied.

These and other objects will be apparent from the following description and in'particular from the detailed description of the various figures of the drawing.

A common type of facsimile system comprises a transmitter embodying means for line by line transverse scanning of a long lsheet of material to be reproduced and a receiver embodying means for similarly recording received signals line by line on a long record sheet. The sheet in both cases is either advanced a line at a time or continuously at the proper rate. Both transmitter and receiver scanners may be driven by synchronous motors. The receiver motor may be operated in synchronism with the transmitter motor by operating it from an alternating current power source common to both or the receiver motor may be operated from alternating current synchronized by means of transmitted synchronizing signals as shown in the patent `entitled Facsimile synchronizing system issued to Hugh C. Ressler essarily center the record on the sheet. The cen- (Cl. 17E-69.5)

tering of the record on the sheet is usually called framing of the record or picture and requires proper phasing between transmitter and receiver scanners. Some synchronizing systems which have been proposed in the past inherently frame a picture when it is synchronized and others inherently synchronize when it is framed.

The present system separates the synchronizing and framing functions atthe receiver a1' though a common signal may be utilized to accomplish both. Framing is required only at the start of reception provided synchronism is continucusly maintained after the framing is completed. The present invention comprises a framing system in which a locally generated impulse complements the synchronizing signal when the receiver is in frame with thetransmitter, maintaining the driving motor in synchronism. When the receiver is out of frame, however, the local and synchronizing signals are not complementary and the driving motor is caused or allowed to change its speed momentarily. Since the driving motor has finite momentum at synchronism, it takes a finite time for it to change speed. As perfect framing is approached, the framing lntervals may become smaller and smaller until they are too small to change the motor speed. To overcome this possibility, means may be provided for limiting the minimum framing effect to a iinite amount.

This invention may be more fully understood from the detailed description of the various iigures of the drawing.

In the drawing:

Fig. 1 shows a schematic diagram of a facsimil receiver embodying one form of the present lnvention.

Fig. 2 shows various waveforms useful in explaining the operation of the present invention.

Figs. 3 and 4 show modified switching systems for framing.

Fig. l shows a facsimile receiver I connected to an antenna 2 and ground 3. A synchronous motor I drives a drum 6 thru suitable reducing gears 5. Drum 6 marks a record sheet 8 by joint action of. electrodes 'l and 9 although the invention is not limited to this method or means of marking the record sheet. On the drum shaft I0 is a cam II which operates an arm I2 opening contact I3 for a portion of each revolution of drum 6. Return spring I4 closes contact I3 during the remainder of each revolution of drum 6. Contact I3 closes the circuitof battery I6 0r other suitable source of power "thru relay coil Il attracting armature`l9 to core I8 and c losing contact 20 completing the power supply circuit of motor 4 thru leads 29 and 30 to switch arms 22 and 23. If arms 22--23 are closed to contacts 24-25, a circuit is completed to the local alternating current power lines which may be for instance 110 volts at 60 cycles. If arms 22--23 are closed to contacts 26-2'|, synchronous currents generated in the receiver or under control of received signals are supplied to motor l. Condenser 28 is provided across contact 2li- I9 to prevent excessive sparking and spring 2| opens contact 20|9 when relay |1-I8 is de-energized.

The system so far described runs synchronously `except for the intervals when contact |3|2 is open, when the power circuit to motor 4 thru contacts |9-20 is opened, dropping the motor speed momentarily. Operated in this manner the phase of each line reproduced by drum i is shifted with respect to the precedingline by a fixed amount.

Ii', now, picture and synchronizing signals are applied across helix 1 and electrode 9 for recording purposes and across relay coil I1 thru isolating resistor I5, the synchronizing signals will prevent relay contacts I9--20 from opening if they pass a steady current thru coil I1, equal to that supplied by battery I6, during the period when contact |2|l is open. This framing sysv tem is intended to operate from signals including flat-topped synchronizing signals of duration slightly greater than the period during which contact |3|2 is open due to cam Fig. 2 shows at A a compositel curve of facsimile picture and synchronizing signals suitable for use in the present system. Flat topped synchronizing signals occupy periods t1 while the picture signals occupy the periods t2 except for small margin periods before and after the signals, in order to prevent possible overlap. Curve B shows the operation of cam |l and switch contacts |2-I3 in which switch contacts |2|3 are closed for periods t4, t and te and open for periods ts. Curve D represents the operation of relay |'l--I8 and contacts |9-2||. Relay |'l-I8 is energized as long as t: and t2 do not overlap and for the full period t4. When the system is badly out of frame as shown at the left of the figure opening contacts |9-20 drops the motor speed as shown in curve C and hence increases the period t4 before the opening of contacts |2|3 again. As shown in an exaggerated manner at the center of Fig. 2, thisimay cause t3 to partly overlap t1 in which case relay I1 is energized for the periods t9 and tio of curve D. The remaining period may be too 'small to shift the phase of the system due to its momentum and hence contacts |9--20 arefdalayed in closing by any well known means for a period tv which is sufficient to always shift the phase of the system a slight amount. Thus period t5 is less than t4 and very nearly equal to normal periods during synchronism of ta. if the operation just described is the final phasing cycle, period t: will fall entirely within t1, and contacts lilwill remain closed due to the cooperative action of synchronizing signals and source I6 as switched in by cam Thereafter the motor by preventing relay contacts |9-20 from opening. Again, once the system is framed, static and other disturbances cause little trouble, since the synchronizing impulses may be made to operate relay contacts |920 before reaching maximum amplitude and hence as long as static does not reduce the impulses below this operation point, they will have no effect on framing.

In Fig. 3 is shown a modified cam-switch and relay system for producing automatic framing. Between power source 22-23 and motor 29-3l are switches |2--I3 and |9-20 connected in parallel. If either switch is closed, power is continuously supplied to the mlotor, but when both switches are open the motor power is interrupted and the motor speed or phase is shifted. Switch |2|3 lsvopened by cam once for each revolution of the scanner drum during the margin interval. If framing signals are being received while switch |2|3 is open, relay switch |8-2 will be closed by the framing pulse and the motor circuit will be continuous. However, if cam-switch |2-l3 opens at any other time, relay |9-20 will also be open and the motor power will be interrupted causing the motor to slow down. The motor is thus slowed down at each revolution of the scanner drum until correct framing is produ'ced from which time on either'fswitch I2|3 or |9-20 will be closed at all times and the motor will be run uninterruptedly in synchronism.l

Fig. 4 shows a modified system in which the two switches are combined in a single switch. Cam. 3| onthe scanner drum shaft allows pin l2 to fall in a slot opening switch 33-34 once for each revolution of the drum. Switch 33-34 is in series between the driving motor and the power source.Y If a framing impulse is received during the time in which pin 32 is traversing the slot in cam 3| switch 33-34 is held closed by magnet 35-31 and the motor power is not interrupted. If framing impulses do not come while pin 32 is traversing the slot in cam 3|, the motor power speed remains constant as long as synchronisml is maintained.

It will be readily seen that once framing is completed, switch Iii-20 ceases to operate, which is an advantage, since it saves wear on it. Also, static and picture signals occurring during out of frame intervals cannot increase the framing error, but can only delay the eventual framing supply circuit is opened and the motor is slowed down. This slowing down is repeated at each revolution of cam 3| until the receiver scanner is in phase with the transmitted signals. Once the system is in phase it Will be noted that switch 33-34 remains stationary and closed whereby minimizing wear and moving parts in the system.

The ,record and framing or synchronizing signal wave forms shown in Fig. 2 will, in general, be transmitted by modulating a sub-carrier which in turn modulates a final carrier. The sub-carrier frequency will depend on the frequency of the record signals which depend on the speed of the pick-up scanner and the resolving power of the electro-optical system. For operation over wire lines the modulated sub-carrier may be transmitted without a final carrier. Also, the sub-carrier frequency may be so chosen that it may be utilized to modulate either a radio telephone or a radio telegraph transmitter.

While one embodiment of the present invention has been shown and described together with a few possible variations, many modications are possible within the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

l. In a facsimile receiving system, the combination of, a facsimile recorder, a synchronizable motor for driving said recorder, means for generating control signals comprising substantially equally spaced unidirectional impulses, means responsive to said impulses for synchronizing said motor, means at the receiver for generating addiational unidirectional impulses substantially complementary in form to said control impulses in accordance with the phase of said motor with respect to said control impulses, and means responsive to both said impulses for varying the phase of said motor to cause the two said im- .pulses to complement each other in their time for generating signals of substantially equal duration and opposite phase with respect t said control signals in accordance with the phase of said motor, phasing means for at least partially controlling the power supply to said motor, and means for temporarily operating said phasing means until said two signals substantially coin# cide.

3. In combination with a synchronizable motor, a source of alternating current of substantially constant frequency, means for operating said motor from at least a portion of said current, means for generating spaced phasing signals, means for reducing said portion of said current operating said motor, a cam operated by said motor for operating said current reducing means, and magnetic means controlled by said phasing signals for preventing the operation of said current reducing means.

4. In combination with a synchronizable motor, a source of alternating current of substantially constant frequency, means for operating said motor from at least a portion of said current, means for generating spaced control signals, means including a switch for reducing said portion bf said current operating said motor, means operated by said motor for periodically operating said switch, a second switch connected in parallel with the rst said switch for preventing said current reduction, and means for operating said second switch from said control signals to prevent said current reduction when said motor rotates in a predetermined phase relation with respect to said control signals.

5. vIn combination with a synchronizable motor, a source of alternating current of substantially constant frequency, means for operating said motor synchronously from at least a portion oi' said current, means for generating spaced control signals, a switch for reducing said portion of said current operating said motor, means controlled by said motor for operating said switch during spaced intervals substantially equal to the duration of said control signals, and means operated by said control signals for preventing the operation of said switch.

l HUGH c. REssLER.

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