US2483442A - Page separation signal and pulse generator - Google Patents

Description

Oct. 4, 1949, J. w. SMITH ET AL ,4

PAGE S EPARATION SIGNAL AND PULSE GENERATOR Filed July 21, 1947 FiG. 2. 15

LTHE TIME NOW IS s-oo M1 0 D/ 4 39 36 Y -o o- FACSIMILE 3 TRANSMITTER 3 FRANK A. HESTER JOHN W. SMITH IN VEN TOR.

ATTORNEY Patented Oct. 4, 1949 PAGE SEPARATION SIGNAL AND PULSE GENERATOR John W. Smith, Long Island City, and Frank A. Hester, New York, N. Y., assignors to Faximile, Inc., New York, N. Y., a corporation of Delaware 7 Application July21, 1947, Serial No. 762,462

8.Claims. (01. 178-695) The present invention concerns electrical systerns and, in particular, synchronizing signal generators suitable for facsimile systems and the like. In practicing the art of facsimile it is common practice to scan a subject copy line by line with a small spot of light reflected or transmitted into a photo-electric cell and to reproduce the signal variations caused by the variations in density of the subject copy as variations in density on a receiving sheet. By thisprocess a reproduction of the original copy is produced provided the receiving mechanism operates in synchronism and in phase with the pick-up scanner. It is thus important in such systems to provide means for accurately synchronizing and phasing the receiving equipment with the transmitting equipment. It is common practice to transmit a synchronizing impulse periodically between lines of scanning, for synchronizing purposes. In order to realize the maximum possible capabilities of a facsimile system particularly when high .detail is desired, the synchronizing impulse must'be accurately shaped and timed with respect to the scanning line. The present invention concerns a simple and highly efiective and accurate device for generating synchronizing impulses, for providing an additional pattern which may be utilized to indicate the end of a page of transmissicn, and for other purposes.

' According to the present invention, a synchronously operated scanning drum having an accurately shaped slot generates a synchronizing impulse in phase with respect to the main transmitting scanner. As an alternative, the synchronizing signal generator of the present invention may be utilized to generate .an accurately timed and shaped synchronizing impulse and-the transmitting scanner proper may be synchronized and phased to this signal in the same way which a receiving scanner is synchronized and phased to a received synchronizing impulse. In addition, the drum which generates the synchronizing pulse has a portion which may be utilized to generate a pattern indicating the end of a page of transmission and may contain additional information such as a time signal or station call letters. This end of the page signal may be fed into the system at any time under the control of a push button or it may be initiated by automatic control means.

It isone object of the present invention to provide a simple, effective and highly accurate means for generating synchronizing signals suitable for facsimile systems and the like.

Afurther object is to provide means for generating a signal suitable for synchronizing, automatic framing and end of page signal.

It is another object of the present invention to provide means for generating a pattern indicating the end of a page of transmission in a facsimile system or the like.

It is a still further object of the present invention to provide means for transmitting time signals, station call letters or other data in combination with an end of the page pattern in a facsimile system or the like.

These and other objects of the present invention will be apparent from the detailed description given in connection with the various figures of the. drawing.

In the drawing:

Fig. 1 shows a view of .a portion of one form of the present invention.

Fig. 2 shows, in a conventionalized form, a typical signal generated by the form of the present invention shown in Fig. 1.

Fig. 3 shows-another view of the form of the present invention shown in Fig. 1.

Fig. 1' shows one view of a portion-of the present invention for purposes of clarity in explainingits operation. A disk :I, having a number of regularly spaced radial slots 2, and mounted on shaft 3, is provided. disk I, may be held in a stationary position or rotated at .a predetermined slow rate of speed under control .of the operator or automatically as will he explained below. Another essential portion -.of the apparatus consists of a drum 4, mounted on shaft 5, and rotated at a rate or speed corresponding to one revolution for each line of scanning in a facsimile system. Drum t has a projecting tab .6, and a slot with an accurately machined straight edge I, as well as window :8. The circumferential length of a tab 6 is made to correspond to the desired width of the synchronizing impulse which is .commonly chosen to be "45 of are. Projected upon the disk I, and drum 4, is shown a slot 1:3 in dotted form to indicate the position of .a photo-electric cell aperture utilized with the system. A scanning spot is formed by the intersection .of :a slot 2, in disk I, and aperturelS. With disk l stationary and drum :4 rotating tab 6 is scanned by this aperture once for each revolution of drum 4. Drum 4 is rotated at a constant rate of speed as will be described later and as it rotates the ac curately machined edge 7 passes the scanning aperture at accurately spaced intervals. If a lamp, not shown, is located :behind scanning aperture 43 and a photo-electric cell, not shown, in front of aperture is a signal will be generated in the photo-electric cell which is constant but with a sudden drop to zero at each passage of tab 6 by the scanning aperture. The upper part of Fig. 2 shows the form of pattern which will be generated, i. e., a pulse extending between lines A and B. Each line is scanned from left to right and the line progression is from top to bottom. This signal may be utilized as the standard synchronizing impulse in a facsimile system with the picture or text occupying the space to the right of the synchronizing signal pattern.

Returning to Fig. 1 the apparatus shown may also be utilized to generate a pattern indicating the end of a page or the end of the transmission. Disk I may be made to rotate at a slow rate of speed, and as it does, the scanning aperture formed between slot l3 and slot 2 scans the remainder of drum 4 consisting of a blank portion and a cut out portion or window 8. The cut out portion 8 may contain a film or stencil imprinted with such legend as The time now is 8:00 p. m. or This is station WWW, etc. The rotation of disk may be initiated at any time under control of the operator or automatically at predetermined intervals and when it has rotated to a position where it has scanned the full width of drum 4 it automatically stops until started again. It accomplishes this in rotating an angular distance equal to the angular distance between slots 2.

Fig. 3 shows an embodiment of the present invention in a facsimile transmitting system. This figure shows drum 4 mounted on shaft 5, rotated by a motor 3| at a predetermined speed. Motor 3| may be any suitable constant speed motor, such as a synchronous motor, and may include speed reducing gears. Motor 3| is supplied with suitable current over leads 32 and 33. The synchronizing impulse generating projection on drum 4 is supplied by a suitable tab such as detachable piece l1 having an accurately ground straight edge |8 fastened to drum 4 by means of screws l9 and 20. Illumination for the scanning system may be supplied by any convenient source such as a long filament lamp 4, focussed by means of lens l5, and reflected by mirror l6 upon aperture l3 in aperture plate 43. Light passed by the scanning process through the intersection of the slots in disk I and slot l3 in aperture plate 43 is iocussed upon cathode 35 of photo-electric cell 34. Scanning signals such as the synchronizing impulse and the end of the page pattern generated in photo-electric cell 34 are passed over leads 31 and 38 to a suitable utilization means such as facsimile transmitter 36 connected to antenna 4| and ground 42. Facsimile transmitter 36 may also transmit picture signals supplied over leads 39 and 40 from a conventional scanner. Slotted disk I, mounted on shaft 3 is arranged to rotate slowly at a predetermined rate so that the scanning of drum 4 will occupy a predetermined number of lines in the final pattern, in response to a control by an operator or to other initiating means. The motion of disk I is imparted by the combination motor and reducing gears 24 connected through shaft '23. Upon the shaft 23 is mounted a stop wheel 2|, having a series of slots 22 corresponding to the position and number of the slots in disk I. A cam-switch 25-26 engages these slots 22 so that when disk I is in the position shown in Fig. 1, switch 25-26 is open and power supplied to motor 24 over leads 21-28 is interrupted. The combination motor and gear arrangement 24 is designed to rotate disk I an amount equal to the angular distance between 4 two slots in a time which will scan the body poi"- tion of drum 4 in the desired time interval. For instance, this may be twenty or thirty lines of scanned copy or any other predetermined amount to indicate the end of a page of transmission and to reproduce properly any time signals or station call letters which it may be desired to transmit. In order to initiate the rotation of disk I and thus the scanning action which it controls, a switch 29-30 which may be controlled by a push button as shown, is closed starting motor '24. As soon as motor 24 starts, the portion of cam-switch 25-26 which rests in the slot 2| moves from the slot to close switch 25-26 and keep motor 24 running until the next slot 2| allows switch 25-26 to open. Switch 25-26 opens whenever the portion 25 falls into a slot 2|. At this point. disk I comes to rest stopping the scanning action until switch 29-30 is again closed. When this cycle of operation has been completed, the synchronizing signal generator continues to enerate a synchronizin impulse by virtue of projection l1 passing the scanning aperture as shown in Fig. 3, or projection 6 as shown in Fig. l and above described. It will be noted that a gap exists preceding the straight edge |8 as drum 4 rotates and hence the leading edge of the synchronizing signal is always accurately defined by the position and time of edge l8. Thus, as edge l8, as shown in Fig. 3, or edge 7, as shown in Fig. 1, is accurately machined, it will generate an accurately timed synchronizing impulse when driven by a constant speed motor 3|. Thisleading edge generates a synchronizing signal at all times and even when the end of the page signal is being generated. I

If it is desired to transmit a complete protected pedestal synchronizing signal (like that transmitted when only tabs 6 or I? control the photocell current) during the time that the end-ofpage signal is being transmitted, the space between the left-hand edge of tab I1 and the dotted line 52, in Fig. 3, may be cut out or otherwise made transparent so as to pass light to the photocell.

As has been described above this end-of-page signal may be initiated at any time by the operator by closing switch 29-36. It may also be initiated automatically at predetermined intervals by means of any automatically operated switch such as commutator switch 46 which being geared to motor 3| through gear box 45 and shaft 44 closes contacts 48 and 49 through spaced segments 41. The gearing and spacing of the segments will evidently determine the spacing of the end-of-page signal. These may be designed to give a uniform page length of eleven inches, for instance, or any other desired uniform length. The automatic control may be utilized by closing switch Ell-5|. V

The system in operation continues to generate a synchronizing impulse as shown in Fig. 2 at all times, even though switch 29-30 is closed. Thus, if the operator wishes to indicate the end of a page or the end of a transmission, he merely closes switch 29-30 starting the second portion of the scanning operation involving the rotation of disk I. When he closes switch 29-30, the motion of disk I scans the body of drum 4 and whatever material may be carried by strip 8. As shown in Fig. 1 strip 8 may be detachable and held in place by tabs 9-|||-| |-|2. Thus, if it is desired to transmit a time signal, for instance,"

a stencil strip showing a given time maybe in-- serted and at the proper instant switch 29-30 may be closed causin disk I to rotate and scan the time indicating strip. .This scanning operation passes signals on through the transmitter to the recorder which then records the time at the proper instant.

It will be seen that the signal generated may be used for synchronizing purposes, framing or phasing and as an end-of-page signal or other boundary signal generator and that it may be utilized in many different ways with either automatic or manual control or a combination of both.

Thus, transmitter 36 serves to combine and send out a composite signal consistin of a continuous line synchronizing and phasing impulse as defined by line A of Fig. 2, facsimile picture signals in the area to the right and above lines B and C, and end-of-page signal below line C, and time or other signal in area D. Or, transmitter 36 may serve to combine and send out a protected pedestal signal, wherein no signal is sent out for the first a pulse for 15, another zero signal for 15 and facsimile picture signals in the remaining 315 similar to those in Fig. 2. In addition to these two methods the form, size, and length of the synchronizing pulse ma be varied, the spacing between signals varied and the number of pulses per scanning line varied by changing or adding more tabs 6 or H.

It will be seen that this synchronous signal generator is simple in construction and accurate in operation. If motor 3i, which may include proper reducing gears or other speed control mechanism, operates at a constant speed and edge 18 is accurately straight a precise and accurately timed synchronizing impulse will be generated. This impulse will be electrical in its generation and will not depend upon mechanical contact or other trouble-producing devices for its operation.

While only a single embodiment of th present invention has been shown and described many variations will be apparent to those skilled in the art within the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. A synchronizing signal and end-of-page signal generator, including in combination a rotatable device including a first portion to represent a desired synchronizing signal and a second portion to represent an end-of-page signal, means for rotating said device at a predetermined rate of speed, means for scanning said first portion continuously to generate a synchronizing signal and switching means for periodically moving said scanning means to scan said second portion to generate an end-of-page signal.

2. A signal generator as set forth in claim 1, wherein said rotatable device includes a drum having a body portion representing the end of page portion and projecting straight edge portion representing the synchronizing signal portion.

3. A signal generator as set forth in claim 1, wherein said end of page portion includes a cut out portion to carry a legend to be scanned to form a part of said end-of-page signal.

4. A signal generator as set forth in claim 1, and including means for automatically stopping the scanning of said end of page portion at the completion of one scanning cycle.

5. A signal generator including the combination of a slotted drum, a tab projecting adjacent to the slot in said drum, means for rotating said drum at a predetermined speed, means for scanning said tab during rotation to generate a signal representing relatively short-time intervals, and means for scanning at least a portion of said drum at predetermined intervals to represent time intervals long compared with said shorttime intervals.

6. A facsimile synchronizing and end-of-page signal generator including in combination, a drum including a main-body, a straight edge slot, and a projecting tab, means for rotating said drum at a predetermined rate of speed, a stationary aperture and a slotted disk positioned adjacent to said drum for cooperatively defining a scanning aperture, a source of light and a photoelectric cell associated with said aperture to generate a periodic synchronizing signal upon each passage of said tab past said aperture, means for rotating said disk to scan the main body of said drum to generate an end-of-page signal and contact means for automatically and periodically energizing said means for rotatin to initiate said last said scanning at predetermined intervals.

7. A generator as set forth in claim 6 and including a cut-out portion in said drum body for containing an end-of-page message.

8. A generator as set forth in claim 6 and including a second contact means for manually initiating the scanning of said drum body.

JOHN W. SMITH. FRANK A. HESTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,227,002 Schlesinger Dec. 31, 1940 2,260,511 Cooley Oct. 28, 1941 2,317,850 Finch Apr. 27, 1943 2,329,077 Nichols Sept. 7, 1943 2,404,571 Finch July 23, 1946 2,416,573 Finch Feb. 25, 1947

Images