US2490126A - Telefacsimile phasing arrangement - Google Patents

Description

Patented Dec. 6, 1949 TELEFACSIMILE PHASING ARRANGEMENT FOR MULTIPLE RECEPTION `Boris F. Grill, Brooklyn, N. Y., afsignor to Times 'Facsimile Corporatior'n,` New York, N. Y., a corporation of New York Application April 5, 1947, Serial No.-739,715

This invention .relates to telefacs-,imile transmission systems and more particularly it relates .t0 phasing controls Lfor such systems.

A principal object of the invention is to provide .ian improved arrangement for phasing one or more facsimile receiving machines which are simultaneously to receive vfrom a common vfac- Simile transmitter,

9 Claims. (Cl. 17,8-695) In certain applications of telefacsimile, for ex.- .4

.ample in newspaper networks, it is not unusual to .transmit the same ,facsimile Subject matter from acommon or central facsimile transmitting station to a series of outlying facsimile receiving Stations, employing `existing public service tele-V T5 `phone .or telegraph lines. Thus, the facsimile :transmitter may be located in one city `and .the facsimile reproductions may be required at `a large number of .distant cities. Obviously, when .existing public service telephone lines are used `to inter-connect the transmitter 4for simultaneous reception at the various outlying stations by s ocalled conference connections, the .costof estab.-` lisjhing and holding the telephone lines isof great concern- Furthermore, at some of the receivingr i stations, it may not be practicable to have an attendant to watch or attend the lfacsimile machine continuously. Therefore, in setting-up a simultaneous transmission network, it is necessary for the transmitting operator to place telewith which the telephone connection is first established must wait until the connections ,are established with the last station of the group. `iuri'lhermore, in order that the yfacsimile ma- Qlllnes at all the connected stations may start ac.- urately in unison, it is necessary for the trans.- ,Intting station to send out, before the actual lacsimile signals are transmitted, a phasing sig@- rnjal so that all the facsimile scanning drums at the outlying stations shall start in unison. Here tofore, it has been the practice in such com ference transmissions for the ,transmitting operator to call each receiving station and inform the attendant thereat that facsimile transmiseach receiving station is required to operate and keep operated, a so-.called phasing button on his I Ilfhine to insure that when the phasing signal is subsequently received afterall the telephone con'-v Fieins Vhave been established, his particular. machine Will be in condition to receive the phas-K,

ing signal. This has necessitated the continued sion is about to take place and the attendant at 2 attendance of the `operators at the stations earlier established in the connection until the complete conference set-up is achieved, In accordance with the present invention, this disadvantage is overcome by providing a novel phasing control at each receiving station so that as soon as the telephone connection is established with any particular station, the attendant thereat merely momentarily presses his phasing button and is not required to hold it operated for any great length of time. Therefore, when the last re:- -ceiving station has been connected in the con-fy ference set-up, the transmitting operator is as;- sured that all the stations are in readiness to -rreceive the phasing signal. i

Accordingly, another principal object of this invention is to provide an improved phasing con, trol arrangement particularly useful where the facsimile receiver is to be started in vphase and operated in unison with one or more distant receivers.

Another object ofthe invention -is to provide an improved phasing control arrangement for facsimile receiving machines generally.

Another feature relates to a phasing control arrangement for facsimile receivers which are to Abe connected in a so-called Iconference circuit with a common transmitter, and wherein all the machines can be accurately Vphased by a single phasing impulse. l

A still further feature relates to the novel or ganization, arrangement and relative intercom' nection of parts which Vcooperate to provide anl improved phasing control arrangement for fac#A simile transmission and receiving systems.

Other features and advantages not particularly enumerated will be apparent after a considera tion of the following detailed descriptions and the appended claims.

. to the invention.

. facsimile transmitting station comprising for eX-1 In the drawing. Fig. 1 represents in schematic circuit form, and

in block diagrammatic vform, the typical facsimiley system employing the phasing control according ample a. scanning drum l I around which the subs ject matter i2 to be transmitted is wrapped. The

drum ll may be provided with a lead screw I3;-I and driven by a suitable motor (not shown) so; -1 that the drum rotates and is simultaneously fed.

axially in the conventional manner. Associated 3 with the scanning drum is the usual scanning head Ill, comprising for example a scanning light source i5, and a pho-toelectric cell I6, whereby the successive elemental areas of the subject matter I2 can be scanned and translated into corresponding facsimile current signals. These signals can then be applied to any well-known amplifier modulator I1, so as to convert the signals preferably into an audio frequency carrier suitable for transmission over the telephone line I8. Before the transmission of the facsimile signals takes place, it is necessary to transmit a phasing signal to the various receiving stations to insure that the scanning drums at these receiving stations start in unison and in the proper phase with respect to the drum II at the transmitter. For this purpose, the drum II may carry at one end a phasing band I which may be white except for a spot Isa which is black, so that When the drum I I rotates for transmitting the phasing signal, a large amplitude phasing signal is transmitted over the line I8. Preferably, the drum Il is provided with a decoupling device so that it can be rotated for phasing without causing axial feed of the drum along the lead screw I3. For a detailed description of a preferred decoupling device for this purpose, reference may be had to U. S. Patent No. 2,138,784.

For purposes of explanation, it will be assumed that the facsimile signals are to be transmitted to a series of facsimile receivingr stations 20, 2I,

22, and for this purpose the attendant at the transmitter I0 places telephone calls in the usual way so as to connect the transmitter I0 via individual telephone lines I8, 23 and 24, to the respective stations. However, the transmitting station does not transmit the phasing signal until the last receiving station has been thus connected. Since the receiving stations 20, 2l, 22, may be identical, only the necessary parts of the station 20 are shown in detail. Thus, station 20 may comprise a receiving amplifier 25, whose output is applied to the recording lamp or stylus 26, which coacts with the recording blank 21 on the scanning drum 28 to reproduce the original shades of the subiect matter I2 in any wellknown manner. The drum 28 is of course arranged to be rotated in synchronism with the drum II during the reproduction of the subject matter, and any Wel1-known synchronizing arrangement may be used for this purpose. For example, the drum II may be controlled in speed by a local tuning fork and the drum 28 may like- Wise be controlled in speed by its local tuning fork.

The receiving drum 28 carries, preferably adjacent one end, a stop arm 29, and associated with this arm is a latch member 30 which is pivotally mounted at point 3l. A tension spring 32 has one end fastened to a xed and grounded support 33, and the other end of the spring is f fastened to the latch 30 so as to tend to rotate this latch to a point where it is in the path of the stop arm 29 as the latter rotates in the direction of the arrow. However, the latch member 30 is of magnetic material and mounted adjacent the lower end thereof is a magnet 34, which is normally energized over a circuit traceable from the positive terminal of any suitable D. C. source such as the battery 35, thence through the normally closed contacts 36 of a push-button switch 31, thence through the resistor 38, and through the winding of magnet 34 to ground. Since the contacts 36 are normally closed, magnet 34 is normally energized and the latch 30 is maintained in the full-line position shown in the drawing. The resistance 38 is proportioned with respect to the current from source 35 so that once the magnet 34 is energized, suiiicient current ows through resistance 38 to maintain the armature in attracted position. However, when the magnet 3l! is deenergized, the said current through resistance 38 from source 55 is not enough to energize magnet 35 suiciently to attract the latch 30 which therefore remains in the dotted line position.

When the telephone connection has been established between the transmitter I0 and the receiver 20, the attendant at the receiver closes the power circuit for the motor 39 which drives drum 28. When the drum 28 has come up to speed, the attendant depresses button 3i momentarily, and this causes magnet 34 to be deenergized, so that on the next rotation of the drum 28 the member 2S engages latch 30 and the drum is stopped, it being understood that a suitable slipfriction clutch (not shown) is provided between the motor shaft and the drum shaft. The facsimile receiver 25 is now in condition to await the reception of the phasing impulse from the transmitter I0. However, it is not necessary for the attendant at receiver 20 to hold the button 31 down. Its momentary operation places the equipment in condition to receive the phasing signal and the attendant can therefore leave the apparatus, since it is in complete condition to receive the phasing impulse and thereafter to begin receiving the facsimile signals.

When the last station of the conference setup is connected via the telephone line, the transmitting operator causes the drum II to be rotated, Without axial traverse, to transmit the single phasing impulse. This impulse is amplied by the amplifier 25 and is applied through the coupling condenser i0 to the control grid 4I of a grid-controlled vacuum tube 52, which may for example be of the pentode type, although any other vacuum tube amplier may be employed. In the conventional way, the grid All is provided with a suitable grid leak resistor 43, and in the conventional Way the shield grid d is connected to the positive terminal l5 of the D. C. power supply through series resistor 5S, and the plate 41 is likewise connected to this D. C. terminal through the coupling resistor t8. In the well; known manner, the suppressor grid i0 is connected to the cathode 50. The plate is coupled through condenser 5I to the control grid 52 o f a gaseous discharge electron tube 53 such as a type 884 Thyratron, having an electron-emitting cathode 54, control grid 52, and a plateor output anode 55. The envelope of tube 53 contains a suitable quantity of ionizable medium and in the well-known manner this tube does not pass current between the anode and cathode until it is red by a suitable potential applied to the control grid 52. The D. C. potential for the plate 55 is derived from the source 35. The resistors 5B, 51, connected between the positive terminal of the source 35 and ground, constitute a voltage divider with the cathode 54 returned to the juno: tion point 58. The resistors 56 and 51 are so proportioned that in the absence of a suitable impulse applied to grid 52, the tube 53 is not conductive. However, when the phasing impulse applied to grid 4I is amplified in tube 42, it apeI plies sufficient potential to grid 52 to render tube 53 current conductive. Resistance 55, for example, may be of 250,000 ohms, and resistance 51 may be of '75,000 ohms.

'.It; shouldbe observed that the- :cathode-toground return circuit of tube e2 is completed through a contact 59 Which is in contact With the grounded latch 33 only when the magnet 34 isdeenergized. In other `vvordsyvv-henythe button 3r'l is momentarily depressed as above described, and the latch 30 engages contact 59, the tube 42 is in condition to relay the phasing impulse to the tube 53. Consequently, when the tube 53y -l'lres or becomes plate current conductive, current ows from the source` 35' through the plate-to-cathode discharge pathv of tube 53, condenser 60 which may be of 2 mfds., and through the Winding of magnet 3d. This current is sufficient` to cause the said magnet to attract the latch permitting the drum 28 to rotate. .As

soon as the latch 3s is attracted by magnetY 34,l

the cathode return circuit of tube 42 is opened, but mag-net 34 remains `sufficiently energized by the current lflow through resistance 38 as above described, to hold the latch 3i! out of the path of stop member 29. Because of the voltage division eiected by resistors 5t, 5l, when the cathode retrrn circuit oi tube :i2 is broken at contact 59, the tube 53 ceases to be plate-to-cathode conductive.

It will be noted that if the attendant should keep the button 3l depressed instead of operating itmomentarily, this will not interfere with the proper phasing since the initial depression of this button releases the latch member 3i! and closes the cathode return 'circuit of tube d2 so that the phasing impulse, When received, causes tube 53 to be red to cause magnet 3G to reattract thevlatch member 39.

Referring to Fig. 2, there is shown a modication of Fig. 1, wherein the magnet 36 does not have to be of the marginal type, and for this purpose an additional electric magnetic relay 6i. is provided. The remaining elements of Fig. 2 are identical withthose of Fig. .1, andthe corresponding parts bear the same designation numerals. Thus, in the system vof Fig. 2, the relay 6l is normally held locked by the current `from the positive terminal of the grounded D. C. sup?- ply source 35, through the normally closed contacts 35 of the push-button switch 3l, resistor 38, armature B2 and front locking contact 63, through the Winding of relay El to ground. The current in this circuit is sufficient to hold the armature 62 in engagement with contact 63 and the armature @il in engagement with .front contact 65. Since the contacts 64 and 55 are normally closed as abovementioned, the circuit through the winding of magnet 34 is likewise completed thus holding the latch member 3i] out of engagement with the stop member 29. However, in this embodiment, the cathode return circuit for tube 42, instead of being controlled by the latch member 33, is controlled by the Contact 59 oi relay 5 l. Thus, when the attendant momentarily depresses button 3l, the locking circuit for relay 6| is broken, and thereupon the cathode return circuit of tube 42 is completed through contact 59 and armature 64. At the same time the magnet 36 is deenergized, the latch member 35i is interposed, under control of spring 32, in the path of stop member 23. When the phasing impulse is received from the transmitter, it is amplied by tube B2 and a sufiicient voltage impulse is applied to the grid 52 of the Thyratron 53 to fire the latter. The plate-tocathode current of tube 53 thereupon flows through the condenser 3l! and it is of suicient amplitude to re-operate the relay 3|, thus reclosing thevcircuit of :magnet 34 and permitting the drum 28 to rotate. Shortly thereafter, the tube 5.3. ragain blocked against plate current conduction vas:described above in connection with Fig. l.

In eachfof the foregoing embodiments, it Will be notedlthat Vduring the actual reception of the facsimile signals, even though a black area should b e scanned,l it. will be ineffective to rere the tubeA 53 because during the actual transmission of the facsimilevsignals, the magnet 34 is held locked through the normally closed contacts of switch '31. In this condition the cathode return circuit of tube -42 'isheld opened, thus effectively disconnecting bothtube -42 and tube 53 from the amplier25.

While 'certain particular embodiments have been describedl herein, it will be understood that variouschanges and rmodilications may be made therein without v'departing from the spirit and scope of thein-vention.

What iscIai-med is:

1. A phasing control arrangement for a rotatable scanning drum and the like comprising, a shiftable drum stopping means, electromagnetic means controlling the shifting of said stopping means, a main energizing circuit for said electromagnetic means, a normally closed auxiliary holding circuit vfor said Ielectromagnetic means and which by itself is ineiiective to energize said electromagnetic means sufliciently to shift said stopping means initially, a manually operable switch in saidV holding circuit and effective in response to its ymomentary operation to break said holdingcircuit and at the lsame time to partially complete saidmain circuit, additional means for fully completing said main circuit, and means to apply a received phasing impulse to render said additional means effective to complete said main energizing circuit independently of the drum rotation andven though said switch has in the meanwhile `beenfreleased regardless of the duration ofoperation of` said manually-operable switch with respect to they time of receipt of said phasing impulse.

2. A phasing control arrangement according to claim l in lwhich .said stopping means includes a pivoted latch, said main energizing circuit comprising the plate-to-cathode circuit of a grid-controlled tube which is normally non-conductive between plate and cathode, the grid of said tube being controlled by another grid-controlled amplier tube Whose plate-to-cathode circuit is completed through said latch, and said electromag- Y netic means comprises a marginal electromagnet Which is arranged to operate said latch.

3. A phasing control arrangement according to claim 1, in which said stopping means includes a pivoted latch, said electromagnetic means including an operating electromagnet for said latch, said main energizing circuit including a phasing impulse amplifier, and circuit connections eiective when said latch is operated by its electromagnet to open the main cathode-to-anode circuit of said amplifier.

4. A phasing control arrangement according to claim 1 in which said stopping means includes a pivoted latch, and said electromagnetic means includes an operating magnet for said latch and a marginal relay for controlling the operating circuit of said operating magnet, said switch being connected in circuit with the winding of said relay, and said main energizing circuit includes the plate-to-cthode discharge path of an ampli- 7 er tube whose electrical continuity is controlled by said latch.

5. A phasing control arrangement according to claim 1 in which the last-mentioned means includes a grid-controlled electron discharge tube who-se plate-to-cathode circuit is opened and closed under control of said drum stopping means.

6. A phasing control arrangement according to claim 1 in which the last-mentioned means includes a grid-controlled electron discharge tube having a cathode return circuit which is completed through contacts opened and closed by said stopping means, and said main energizing circuit includes a grid-controlled gaseous discharge tube whose conductivity is controlled by the output of said electron discharge tube.

7. A phasing control arrangement for facsimile scanning drums and the like comprising, a pivoted latch for selectively stopping said drum, an electromagnet for operating said latch, a locking circuit for said electromagnet which -normally receives insufficient current to operate said latch, circuit contacts which are open when said latch is operated by said magnet to permit said drum to rotate, said contacts being closed when said magnet is deenergized to stop said drum, normally closed but manually operable switch contacts which control said locking circuit, a gridcontrolled electron discharge tube amplifier upon which a drum release impulse is impressed, said tube having its plate-to-cathode circuit completed through said circuit contacts, and means responsive to the impression of said drum release impulse to apply operating current to said electromagnet, said circuit contacts completing the continuity of the plate-to-cathode circuit of said grid-controlled tube to render it effective as an mplii'ler even though said manually operable switch contacts have in the meanwhile been operated to break said locking circuit.

8. A phasing control arrangement for a facsimile scanning drum and the like, comprising a shiftable member arranged to move into and out of stopping engagement with said drum, an electromagnet for controlling said member, a normally incomplete main energizing circuit for said electromagnet, means eiective upon the receipt of an electric phasing impulse and while said electromagnet is deenergized to complete said main energizing circuit and independently of the engagement betwen said member and drum, a normally-closed holding circuit for said electromagnet to maintain said member out of stopping engagement with said drum after the receipt of said phasing impulse, a push-button switch for momentarily opening said holding circuit to complete said main energizing circuit immediately upon the receipt of said phasing impulse and independently of Whether said button is held operated at the instant the phasing impulse is received.

9. A phasing control arrangement for a rotatable scanning drum and the like, comprising a latch member for stopping the drum, electromagnetic means for controlling said latch member to release the drum for rotation When said means is energized, amplifier means for producing a phasing pulse for operating said electromagnetic means, means for rendering said last-mentioned amplier means operative including contacts which are closed whenever the latch member is released and opened whenever the electromagnetic means is energized to release the drum for rotation, said contacts being in circuit withsaid amplier means, and means including a manually-operable switch for deenergizing said electromagnetic means to close said contacts in readiness for phasing in response to only a momentary operation of said switch and ineiective to re-open said contacts when it is returned to normal after being operated.

BORIS F. GRIB.

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

UNITED STATES PATENTS Number Name Date 2,212,971 Finch Aug. 27, 1940 2,275,249 Cooley Mar. 3, 1942 2,309,622 Anderson Feb. 2, 1943 2,329,077 Nichols Sept. 7, 1943

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