US2483449A - Facsimile transmission system - Google Patents

Description

Oct. 4, 1949. R. J. WISE ETAL 2,483,449

FACSIMILE TRANSMISSION SYSTEM Original Filed April 18, 1941 2 Sheets-Sheet 1 TM EJ FIG. I AC [4 I2 :7

AMPLlFIER MESSAGE IN DEPOSIT BEING MESSAGE USE MESSAGE TRANSMITTED ACCEPTED RECTIFIER 2'7 JNVENTORS R. J. WISE G. H. RI 0| NGS R. o. PARROTT ATTORNEY Patented Oct. 4, 1949 FACSIMILE TRANSMISSION SYSTEM Raleigh J. Wise, Dunellen, Garvice H. Ridings, Summit, and Robert D. Parrott, West New York, N. J., assignors to The Western Union Telegraph Company, New York, N. Y., a corporation of New York Original application April 18, 1941, Serial No.

389,164. Divided and this application December 9, 1944, Serial No. 567,418

36 Claims.

Our present invention relates to facsimile transmission systems and its object is to provide novel connections between the transmitter and the recorder for the automatic control of the recorder from the transmitter. This does away with certain manual operations heretofore required at the recorder in systems of this type. Conversely, certain operations at the recorder react automatically on the transmitter for controlling certain functions of the latter, as will be apparent from the description to follow.

According to one feature of this invention, the connection of the recorder to a source of power is automatically controlled by a carrier current generated by the transmitter. In other Words, the recorder operates only during the period of generation of the carrier current. Upon cessation of the latter, as when the end of the transmitted message is reached, the recorder is automatically disconnected from its source of power. j

This simplifies the practical use of our system.

In a preferred form of our invention we provide means for enabling the attendant at the recorder to make one or more copies of the transmitted message. For this purpose the attendant simply operates a switch and the system automatically transmits the message again for another recordmg.

We may also provide means for selectively conditioning the system to transmit a single message or a series of messages deposited one after the other as each is recorded. That is, oursystem can be set for intermittent operation or for continuous operation, and this control is effected by merely operating a switch at the transmitter.

The foregoing and other features and advantages of our invention will be apparent from a description of the accompanying drawings, in which:

Fig. 1 is a wiring diagram of the control circuits associated with the transmitter; and

Fig. 2 is a diagram of the circuits associated with the receiver or recorder.

In these diagrams we have shown only such elements of the transmitting and recording apparatus as are necessary to explain the operation of the control circuits, which may be combined with any practical form of transmitter and recorder. For example, a suitable construction of transmitter and recorder is disclosed and claimed in our copending application Serial No. 389,164, filed April 18, 1941, now Patent No. 2,365,741 granted Dec. 26, 1944, of which the present case is a division.

In Fig. 1 (upper left corner) the transmitter mechanism TM is represented by a scanning cylinder ID on which a message sheet I2 is properly mounted for the transmission operation. For convenience we shall speak of the subject matter on sheet I 2 as a message, but obviously it may be any kind of intelligence adapted to be put on paper or like material, like a drawing or a picture. In shop parlance, the message sheet is usually referred to as copy. A suitable scanning carriage 53, shown in the lower left corner of Fig. 1, is operatively associated with cylinder l0 and carries the usual parts for scanning the message sheet !2. It will be suflicient to show an exciter lamp hi, a photocell l5, interposed lens systems I6 and H, and a light interrupting disc or chopper It. The disc l8 has peripheral holes or notches IQ for the interrupted passage of light to the photocell l 5. A motor 20 rotates the cylinder l0 and moves the scanning carriage l3 axially of the cylinder through suitable driving con nections. Another motor 2| rotates the chopper disc is at the proper speed to produce the desired carrier frequency.

In the operation of the transmitter TM a beam of light emitted by lamp I4 is condensed by lens l6 to a small spot on cylinder ill or sheet 12 if the latter is mounted on the cylinder. The light reflected from that spot is directed by condensing lens l'l' through the peripheral holes or notches of disc Hi to photocell I5. The output of this cell is passed through an amplifier 22 and impressed upon a pair of line conductors LI and L2.

As will be understood, the action of exciter lamp [4 on photocell l5 generates a carrier current of a frequency depending upon the rotary speed of disc [8 and the number of its peripheral notches. The light reflected from the cylinder itself or from the background of the message sheet generates a carrier current of even tone and maximum value. When the scanning spot strikes the message bearing portion of the sheet, the carrier current will be modulated in accordance with the tone values of the copy.

Turning to Fig. 2, the receiving or recording mechanism RM is represented schematically by a rotary cylinder 23 and the recording stylus 24. The latter is suitably mounted for scanning movement in contact with the recording blank 25 on cylinder 23. It should be understood that when no recording is being done, the stylus is dissociated from the cylinder. For convenience we have assumed that the recorder RM is of the electro-chemical type, so the stylus 24 is connected on in the recorder circuit. The recording cylinder 23 is operated by a motor 26 (see lower left corner of Fig. 2) through suitable driving connections, and this motor may also operate the scanning carriage in which the stylus 24 is supported. The mechanical connections between the motor 28 and the parts 23 and 24 need not be shown or described because such details do not form part of this invention and will be understood by those skilled in the art.

At the receiving station the line conductors Ll and L2, which carry the facsimile signals or impulses generated by the transmitter, are con-- nected in multiple to a signal inverter 21 and an amplifier 28. The inverter 21 is connected to an amplifier 29 which is coupled through a trans former 3G to the recording circuit of stylus 24-. By reason of its connection to line conductors Li and L2, the amplifier 28 passes all of the facsimile signals to control the operation of a relay 3i, the function of which will be described in due course.

The source of power for the transmittingstation and the receiving station is indicated by a pair of bus bars A and B for each station. In this instance the source of power is alternating current. When the system is idle, the transmitting and receiving stations are not connected to their respective sources of power.

Suppose a person wishes to transmit a message inscribed on a suitable blank provided for that purpose. Before the copy can be deposited in the machine, it is necessary to operate a push button 32 at the transmitter. This energizes the relay 33 through a circuit extending from bus bar A through the winding of the relay, push button contact 34, wire 35 to point 36, Wire 31, and through the break contact 38 of a relay 39 to the bus bar B of the alternating current supply. The energized relay 33 closes its contact 48 which is connected in parallel with push button contact 34, so that the rela becomes locked and permits release of the push button.

The make contact M of energized relay 33 connects one terminal of a relay 42 to bus bar A through a wire 43, and a wire 44 connects the other terminal of relay 12 to bus bar B. The relay 32 is thus energized to move its armature 45 downward for actuating a plurality of switch contacts associated therewith. The closure of one of these contacts 45 connects the main bus bar A to a secondary bus bar A. Connected between bus bar A and bus bar B are the exciter lamp M, the driving motor 29 for the scanning cylinder I8, and the motor 2| for driving the light chopper disc 18. As previously mentioned, the motor 20 also operates the driving connections, usually including a feed screw, for the optical scanning carriage l3.

It will thus be seen that the optical scanning mechanism of the transmitter is energized for operation before the deposit of the message intended for transmission. The exciter lamp l4 causes the photocell I to generate an unmodulated carrier current of maximum amplitude by the reflection of light from cylinder Hi. This carrier current is transmitted through amplifier 22, which is always conditioned for operation, over the line conductors LI and L2 to the receiving station. I

The received signals, suitably amplified by amplifier 28 and being of maximum amplitude, cause the operation of relay 3|. Through a make contact 4? of this relay the input circuit of a vacuum tube 48 is energized to close the plate circuit thereof, thereby energizing a relay '49 connected in series with the output circuit of the tube. The closure of make contact 50 of relay 49 connects a transformer 5| to the source of power through the following circuit from bus bar A, switch 52, contact 50, wire 53 to point 54, wire 55 to point 55, through the primary winding 56 of transformer 5i, wire 51, closed contact 58, and wire 59 to bus bar B. The function of transformer 5| is to energize an exciter lamp 60 connected to the secondar winding Bl, as shown in the lower right corner of Fig. 2. The closing of contact 50 also energizes the motor 26, which operates the recording cylinder 23 and the scanning carriage of stylus 24.

The switch 52 in the main power line may be controlled by a hinged panel of the recorder cabinet and is held closed until the panel is opened for access to the apparatus inside, whereupon the switch is automatically released to cut the power off. So far as the operation of this system goes, the switch 52 may be omitted and we mention it here only because it is described in our parent application.

If it be assumed that the recorder is in such condition that there is no recording blank in position to be placed upon cylinder 23, then the light from lamp 60 falls upon a photocell 62, thereby energizing the output circuit of a vacuum tube 63. A relay 64 connected to the output circuit of this tube becomes energized to close its contact 65, thereby connecting one terminal of the blank feed motor 66 to the bus bar B. The other terminal of this motor is connected to bus bar A through wires '55 and 53, the closed contact 50 of energized relay 49, and the panel switch 52.

The operation of feed motor 68 conveys one of the recording blanks '25 from a supply roll 61 into a pcmition for mounting on the recording drum or cylinder 23. In this preliminary position the blank 25 rests on a suitable support 68 between the exciter lamp 6!] and the photocell 62. The light falling on the photcell is thus interrupted and the vacuum tube 63 becomes inoperative, thereby releasing the relay 64 and stopping the feed motor 66.

We might mention that since the blank feeding mechanism associated with the recorder does not in and of itself form part of our present invention, we have not considered it necessar to show or describe any structural details thereof. Our parent application discloses a blank feeding mechanism suitable for use in connection with the system herein set forth.

When the relay 64 is released at the stopping of the blank feeding mechanism, as just described, a positive direct current potential is applied to the line conductor L2 through the following connections: from the positive terminal 69 of a direct current source, contact 10, wire ll, contact 12 of relay 64, wire 73, contact H, wire 15, and through closed contact 16 of relay 49 to line conductor L2. Let us see what effect this has on the transmitter.

Referring to Fig. 1, there is a three-position polar relay TI connected to line conductor L2. The armature 18 of this relay lies normally between two contacts 19 and 8B. In response to positive potential applied to line conductor L2, the armature T8 is moved to contact 19. A circuit is thus provided for the operation of relay 8], eitending from bus bar A, wire 82, armature 18, contact 19, through the winding of relay BI, and wire83 to bus bar 13. Closure of the make contact 84 of relays! energizes alockin'g solenoid 85 through the following circuit: from bus bar A,

wire 82, closed contact 84, wire 86 to point'81, through the winding of solenoid 85, and wire 44 to bus bar B.

The energized solenoid 85 moves its armature 88 to the left over the adjacent armature 45 which has previously been moved downward by the energized relay 42. In this way the solenoid 85 locks the armature 45 and its associated switches to operated position, even when the relay 42 is denergized. At the same time the make contact 89, closed by the operation of locking armature 88, connects the winding of solenoid 85 to one blade 90 of a double-throw switch indicated as a whole by DS. This switch has a second blade 9|. When the switch is thrown to the right, the blade 90 engages a contact 92, but the blade 9I is idle. Throwing the switch to the left moves the blades 90 and 9| to contacts 93 and 94, respectively.

The purpose of switch DS is to condition the system for either intermittent or continuous operation. That is, either for a single message or anumber of successive messages, as will be explained in detail hereinafter. At this point we need only mention that the switch is thrown to the right for intermittent operation of the system and is thrown to the left for continuous operation thereof. I For the present we shall assume that the switch DS is in its right-hand position with the blade 90engaging the contact 92. The winding of solenoid 85 is thus connected to bus bar A through closed contact 89, switch blade 90 and contact 92, closed contact 95 of a relay 96, wire 91 to closed switch contact 98, and through wire 99 to bus bar A. This connection permits the subsequent release of relay 8| and insures that the switch contacts previously operated by the armature 45 of relay 42 remain locked in closed position as long as relay 96 is not energized.

The closing of make contact I00 of relay 8| energizes a relay IOI (see lower central part of Fig. 1) through the following circuit: from bus barA, wire 82, relay contact I 90, switch contact I02, wire I03, through the winding of relay IOI, wire I04, switch contact I05, and wire I08 to bus bar B. The contact I05 is controlled by a movable switch arm I01 arranged to engage the scanning cylinder I0 to detect the presence or absence of a message sheet on the cylinder. In Fig. 1 the arm I01 closes the contact I05 because the copy or message sheet has not yet been deposited in the transmitter.

We have not shown any structural details of the mounting and arrangement of switch arm I01 in the transmitter scanning mechanism because they form no part of our present invention, such details being shown in our parent application, previously identified. It is sufficient to point out that when there is no copy on cylinder I0, the arm I 01 is down and closes the lower contact I05. However, with a sheet mounted on the cylinder, the arm engages the sheet and is raised to close the upper contact I08 for a purpose that will be explained later.

The energizing of relay IOI closes its make contact I09 and thereby connects a magnet IIO to the power circuit as follows: from bus bar A through closed contact 46 to the secondary bus bar A, through the winding of magnet IIO, wire II2, make contact I09, and wire II3 to bus bar B. At the same time the circuit of lamp I I4 is closed from bus bar A, wire II5, through the lamp ,to wire II 6, which is connected .to wire II2, and

from there to bus bar B. The lighted lamp II4 illuminates a sign saying Deposit message.

The transmitter cabinet has a chute II1 for receiving the prepared message sheets. When the magnet I I0 is not energized, the cover I I8 carried by the armature or plunger of the magnet closes the chute II1. Upon being energized, the magnet withdraws the cover I0 and opens the chute. This operation is visibly proclaimed by the lighted lamp II4 which tells you that now is the time to deposit the message. The interval between operating the push button .32 and clearing the machine for deposit of the message is only a few seconds, during which the system is automatically conditioned to transmit and record the message. The deposited message sheet is conveyed in any practical way to the rotating cylinder I0 and supported thereon for the scanning operation.

As soon as sheet I2 is mounted on cylinder I0, the arm I01 is raised to break the lower contact I05 and close the upper contact I08. The opening of contact I05 breaks the circuit of relay IOI, whereby the contact I09 is opened to break the circuits of chute magnet I I0 and lamp I I4. This extinguishes the Deposit message sign and closes the chute III to prevent the insertion of other sheets. The closing of contact I08 by switch arm I 01 energizes a magnet II 9, which connects the scanning carriage I3 for operative movement axially along the cylinder I0 by the driving motor 20. The circuit of magnet I I9 goes from bus bar A to wire 82, contact I00 of relay SI, switch contact I02, wire I03 to point I20, through the winding of magnet II9, wire I2I, contact I 08, and wire I06 to bus bar B. A lamp I22 is connected in parallel with the magnet II9 through wires I03 and I23. 'This lamp illuminates a sign having the legend Message being transmitted.

When the magnet H9 is energized, it closcs'its make contact I24 which is connected by a wire I25 to the positive terminal of a rectifier I25. The negative terminal of this rectifier is connected to contact 94 of switch DS, but at this time the switch is in right-hand position, so the contact 94 is not in any circuit. The rectifier I25 is connected to bus bars A and B, but the input circuit of the rectifier is not closed unless the switch contact 46 is in closed position, as it is now. The closing of contact I24 causes positive direct current potential to be impressed on line conductor LI through the followin connections: from the positive terminal of rectifier I26, through Wire I25, contact I24, wire I21, break contact I28 of relay 39, wire I29, break contact I30 of relay 98, and through connection I3I to conductor L I.

Turning now to Fig. 2, let us see what happens at the recording station when the line conductor Ll receives the positive potential of rectifier I26. A three-position polar relay I32 is connected to conductor LI by wire I33. The armature I34 of this relay normally lies between two contacts I35 and I36. In response to the positive potential on line conductor LI, the armature I34 engages contact I35, whereby a relay I31 is energized to operate its contacts. The circuit of relay I31 goes from but bar A to closed contact 50 of energized relay 49, wire 53 to point I38, through armature I34 and contact I35, wire I39, through the winding of relay I31, Wire I40, and wire 59 to bus bar B. The make contact I4I of relay I31 is connected to shunt the break contact 12 of relay 64 for a purpose to be more fully deassume scribed. Eventhough the break contact M of the energized relay I31. is opened, the transformer it remains energized: through themake contact I42 ofrelay I31 and the break contact-143 of a relay I44.

With the message sheet I2 in position on cylinder I of the transmitter, the scannin operation begins. Before the light point from excite): lamp I4 reachesthe message itself, a. black spot I45 printed on the sheet is scannedt generate-a carrier current signal ofv minimum amplitude. The reception of thissignal. at the recorder mo.- mentarily deenergizes relay 3I. In other. words, the scanning of spot I451 on the message. sheet produces such modulation of. the carrier current signal as to: cause the deenergization. of relay 3| for a sufiicient interval to close its break contact I46. A circuit is thus completedfor the operation of relay I44, extending from th positiveterminal I41 of a convenient source of. direct current through the break contact I48 of. a relay I49, wires I50 and Il,.through the winding of. relay I44, wire I52, break contact I of relay 3|,wire I53, and through the make contact I54 of energized relay I3! to ground; The closingofmake contact l55' by relay I44 locks this relay in energized condition, so that upon the re-operation of relay 3I in response to carrier current signals of greater than the minimum amplitudathe relay I44 is maintained energized independently of relay 3|. The opening of break contact I43 of relay I44 deenergizes the transformer 5| and extinguishes the eXciter lamp 60.

Th energized relay I44 closes another make contact I56 to complete a direct current circuit from a convenient source through a magnet I5 1, which is assumed to be properly mounted in the recording mechanism. This magnet actuates a roller I58 which forces the blank 25 from its preliminary position, as indicated in Fig. 2; into a position where it is gripped by the recording cylinder 23 and wrapped around it in recording position. The removal of blank 25 from between the lamp 5E and the photocell 62 does not produce any result at this time, because the lamp-is'extlnguished.

The recording mechanism has a movable switch arm I59 arranged to rest on the cylinder 23when no blank is mounted thereon. Inthislower'position of arm I59, the associated contact IE0 is open. As soon as the advancing edge of the blank wrapped around cylinder 23 reaches the arm, the latter is raised to close the contact I80 This operation connects the winding of. relay I49 to the source of power from bus bar A, contact wire 53 to point 54, wire 55, relay I49, contact I530, switch arm I59, and Wire IEI to busbar B.

The energized relay I49 opens itsbreakcontact I48 and thereby deenergizes the rela I44. However, the condenser I52 connected inzparallel with relay I44 is of sufficient size to delay: the release of the contacts of this relay until the recording blank 25 is fully mounted on. cylinder 23. After this operation has been completed, the contacts of relay M4 are released, thereby deenergizing the magnet I51. The closure of; break contact I43 of relay I44 again energizes the transformer El and operates the light Iii] to: excite the photocell 62. This initiates the'operation of the blank feeding motor 66 to convey another blank into position to be transferred to-the recording cylinder when required. The excited photocell 62 also energizes the relay 64' which opens the break contact I2 and disconnects the latter from the positive terminal: fi9=ofa source ill) 8. of direct current potential. However, this:potenti'ali is not disconnected from the line conductor L2 because of the shunt path provided-through themake contact I14 I. of relay I31.

Another function. performed by the operation of relay I49; in response to the mounting of the recording blank on cylinder 23' is the energization of. two. magnets I63. and IE4, which are connected in. parallel. The circuits of these magnets can be traced from bus bar A through closed con.-

tact 50, wire 53 to point. I65, wire I66, through the windings of both magnets, wire IG'L, make contact I68 of relay I49; and wire IEI to busbar B. These two magnets when energized place the recording stylus 24 in operative condition through any practical connections, not necessar to show or describe. Let it suifice to say that the magnet I63 adjusts the stylus into recording contactv with the blank on cylinder 23 and the magnet I.64-conmeets the scanningcarriage of the stylus with the driving motor 26.

We now have the recorder in condition for receiving the message from the transmitter. As the facsimile signals generated at the transmitter are received at the recorder, they are applied, after inversion and amplification, to the recording blank on cylinder 23 for: reproduction of the sub.- ject matter that is being scanned at? the transmitter. These signals also are applied to the relay 3 I, which responds in accordance with the'signa1- modulations produced by the scanned, message. In the illustratedembodiment, the two armaturesof relay 3| will vibrate as the amplitudeof the signal varies between maximum and minimum values. However, the closure of the breakcontact I46 of relay 3I isineffective to operate the relay I44 because theoperating circuit of. the latter relay is open at the break. contact I48 of the energized relay I49.

The opening and closing of contact 41 of the vibrating relay- 3I alternately energizes and deener-gizes the input circuit of vacuum tube 48,,but this circuit is provided with means for delaying the. deenergizationthereof during the interval'of time that the relay contact 41 is open. This is accomplished by providing a condenser I 69 between the gridor" the tube'and a source of negative potential; Whenthe contact 41 is closed, thiscondenser is charged to a potential whereby the input circuit of thetube 48 is energized. As soon. as the contact 41 is opened, the charge on the. condenser begins to dissipate through a-leak resistor I10. After the lapse of a predetermined time. the potential of the grid of tube 48 becomes sufiicientlynegative with respect to its cathode wherebythe plate current is reduced to a value which:is.insufiicient to maintain the relay 49in energized condition. However; the values of condenser IBQand-leak resistor I'Ill. areso chosen that the plate circuit of tube 48 draws sufficient cur-- rent during'the normaloperation of recording to keepthe :relay 49'energized.

At the'transmitter, when the carriage I3 cone taining the scanning apparatus has advanced to the end of' its movement after transmission of the message, the contact III operated by the carriage is closed, thereby closing acircuit from bus bar; A through the winding of relay 3&- and through the break contact I12 of relay II to bus bar B; The relay 39' is thus energized to openitszbreak'contact I'28'and thereby disconnect positive potentiatfrom the line conductorlil. It Willi be remembered that this positive potential was previously applied toconductor Ll whenthe 9 magnet II 9 was energized to connect the scanning carriage I3 for operative movement.

At the recorder, the disconnection of positive potential from the line conductor LI disengages the armature of polar relay I32 from its contact I 35 and thereby opens the operating circuit of relay I31. The release of this relay closes a circuit from positive potential at I41 through the make contact I13 of energized relay I49, wire I14, through the winding of relay I15, wire I16, and the break contact I11 of deenergized relay I31 to ground. The operation of relay I15 closes a circuit through its make contact I18 to connect the winding of the blank stripping magnet I19 between the bus bars A and B.

It is assumed that the energized magnet I19 operates suitable means, not necessary to show or describe, for stripping the record bearing sheet from cylinder 23, whereby the switch contact I 60 is opened. The relay I49 is thus released and the closure of its break contact I80 completes the power circuit through a relay I8I (at the bottom of Fig. 2) as follows: from bus bar A, contact 50 of energized relay 49, wire 53 to point I82, break contact I83 of a relay I 84, wire I85, the normally closed contact I86 of a key switch I81, wire I88, through the winding of relay I8I, wire I89, make contact I90 of energized relay I15, wire I9I, break contact I80 of relay I49 (now released), and wire I 6| to bus bar B. The operation of relay I8I closes its make contact I92, whereby the relay is locked in energized condition. At the same time a lamp I93, connected in parallel with relay I8I, is lighted to signal the attendant at the recording station that a message has been received. The lamp I93 thus operates as the End of message signal for the recording station.

Still referring to Fig. 2, it will be observed that the operating circuit of the stripping magnet I19 includes the make contact I18 of relay I15, which 4 is deenergized by the opening of make contact I13 of relay I49 when the latter is released by the opening of contact I upon removal of the record bearing sheet from cylinder 23. However, the relay I15 is provided with a condenser I 94 connected in parallel with its winding and this condenser delays the release of contact I18 until after the sheet has been completely removed from the cylinder.

While these functions are being performed at the recorder, it should be pointed out that immediately upon the operation of relay I15 the positive potential which was connected to line conductor L2 during the recording operation is removed therefrom by the opening of break contact 10 of this relay. Also, by the time this con tact is permitted to reclose upon the deenergization of relay I15, the circuit of this positive potential is opened at the break contact 14 of relay I8 I, which has operated in the meantime.

At the transmitter the removal of positive po tential from conductor L2 produces a response in the polar relay 11 whereby its armature 18 disengages the contact 19 and thus releases the relay 8I. The opening of make contact I00 of this relay deenergizes the scanning magnet II9, thus opening the contacts controlled thereby and permitting the return of carriage I3 to its original position.

As long as the magnet II9 of the transmitter is energized during a scanning operation, its make contact I94 is closed and shunts the break contact 30 of relay 39. Therefore, when the latter is energized to open its break contacts in response to the closing of the carriage control con- I tact I H a locking circuit for the relay 33 is maintained through the magnet contact I94. But when the positive potential is removed from line conductor L2 upon receipt of the end-of-message signal I 93 at the recorder to release the relay 8| at the transmitter and thereby release the scanning magnet II 9, then the make contact I94 of this magnet is opened to deenergize the relay 33. This relay remains in that condition until the push button 32 is again operated.

We now have come to the point where the received message has been stripped from the recording cylinder 23 and is in the hands of the attendant at the recorder. Suppose the attendant for any reason wants to make another recording of the same subject matter. To do this it is only necessary to move the handle of key switch I81 momentarily to the right. This opens the contact 186 andreleases the relay I8I, at the same time extinguishing the lamp I93 which signaled the end of the message. The release of relay I8! again connects positive potential through its break contact 14 to the line conductor L2. At the transmitter, where the message is still on the scanning cylinder, the polar relay 11 is again operated to close the lower contact 19. The transmitting mechanism is thereby started upon the same cycle of operation as pre viously described to make a second recording of the message. Obviously as many copies of the same message can thus be made as are required.

When the attendant at the recorder has made suflicient copies of the message, he throws the handle of key switch I81 to the left to close a contact I95. This energizes a relay I96 through the following circuit: from bus bar A to wire I88, as previously described for relay I8I, through the winding of relay I96, switch contact I95, and through make contact I92 of relay I8I to bus bar B. The relay I96 is thereby operated and is locked in energized condition through its make contact I91. Closure of the make contact U98 of relay I96 connects negative potential to line conductor L2 from the negative terminal I99 of a source of direct current through contact I98, make contact 200 of energized relay I81, wire 15, and through make contact 16 of relay 49 to line conductor L2.

At the transmitting station the negative po- 1 tential connected to the line conductor L2 causes the armature 18 of polar relay 11 to engage the contact 89. A circuit is thus established from bus bar A through wire 82, relay contact 80, wire 20I, switch contact 202, through the winding of a blank stripping magnet 203, and through wire 83 to bus bar B. A lamp 204 connected in multiple with magnet 203 is also energized to illuminate a sign bearing the legend Message accepted. When the magnet 203 is energized, it

operates suitable means for stripping the message sheet I2 from the scanning cylinder I0 of the transmitter. A practical form of blank stripping means being disclosed in our parent case, we need not say anything more about it here.

, It should be noted that the scanned message is not stripped from the transmitting cylinder until the attendant at the recorder operates the switch I81 to the Accept position.

Still referring to the transmitter, as soon as the message sheet I2 has been removed from the cylinder I9 after the transmission and acceptance of the recorded copy, the switch contact I05 is reclosed to establish a circuit from bus bar A, wire 82, contact of polar relay 11, wire 20I to point 205, wire 206, through the winding of relay 96, wire 201, break contact 208 of relay IOI, wire I94, and through contact I to bus bar B. The relay 96 is thus energized and opens the break contact 95, thereby opening the looking circuit of solenoid 85. The armature of relay 42 is thus released and permits the associated switch contacts to resume their respective normal positions.

The opening of contact 46 disconnects the auxiliary bus bar A from the main bus bar A, thereby deenergizing the rectifier I26, the driving motor 29 of the scanning mechanism, the motor 2| that drives the chopper disc I8, and the exciter lamp I4. In other words, the removal of the message from the transmitting cylinder automatically disconnects the scanning apparatus of the transmitter from the source of power.

The release of armature 45 of relay 4?. closes a circuit from bus bar A through wire 99, switch contact 209, wire 2I9, make contact 2II of energized relay 96, wire 2I2, and the switch contact 2I3 to reenergize the locking solenoid 85. The operation of the solenoid armature 88 at this time prevents the movement of armature 45 in response to any possible reenergization of relay 42. If we connect several transmitting stations to a single receiving station, we may provide each transmitting station with a lamp 28 to illuminate a sign In use as a warning or busy signal to the idle stations that one of the transmitters is being used. In that case the solenoid 85 is energized at the idle stations and locks the armature of relay 42 in normal open position during the busy or In use period. In the present instance the lamp 2I4 is energized simultaneously with solenoid 85 through the closed switch contact 2 I3.

When the scanning apparatus of the transmitter is deenergized upon release of the switch contacts controlled by relay 42, the generation of carrier current ceases. At the recorder the absence of carrier current signals causes the release of relay 3|, and at a predetermined time following the release of this relay, the timing apparatus associated with the input circuit of vacuum tube 48 becomes efiective to open the plate circuit and cause the release of relay 49. The opening of contact 59 of this relay disconnects the driving motor 26 and the primary winding 56 of transformer 5| from the bus bar A and also deenergizes the relays I8I and I96.

In this way the recording apparatus is automatically disconnected from its source of power and is restored to normal idle condition, in which it remains until the push button 32 at the transmitter is again operated. The opening of relay contact 59 also disconnects negative potential from the line L2, which restores the polar relay I! at the transmitter to normal condition and thereby releases the relay 96 to deenergize the solenoid 85 and the In use lamp 2M.

In the present embodiment of our invention we also provide means for adjusting the system to transmit a message without waiting for the scanning carriage I3 of the transmitter to reach the end of its normal path of travel. Such a facility is for the purpose of economizing on line time utilized for the transmission of facsimile signals when a relatively short message is to be transmitted. To this end the transmitter is provided with a switch 2 I5 (at the bottom of Fig. 1), which has a handle accessible from the outside of the machine. In the case of a short message, you move the switch handle to the right. The switch is I2 locked in this'position by energization of a magnet 2 I6 through a circuit which extends from bus bar A through the winding of the magnet, its make contact 211, and the break contact 33 of relay 39 (not energized now) to the bus bar B.

The scanning and transmitting operations take place as previously described until the carriage 13 has traveled a sufficient distance to close the contact 2 I8. This may be effected in any practical Way, as by a roller 2I9 mounted on the carriage in the path of a suitable member 229, which is adapted to engage the roller and move the contact 2I8 to closed position. This occurs before the carriage is at the end of its normal scanning movement but after scanning of a short message is completed.

The closure of contact 2I3 completes an operating circuit for the relay 39 extending from bus bar A through contact 2I8, wire 22I, contact 222 of switch 2I5, through the winding of relay 39, the break contact I12 of relay NH, and through wire I I3 to bus bar B. When the relay 39 is energized, it opens its break contact I28 and disconnects the positive potential from line conductor LI to control the recording mechanism in the manner already described. The opening of break contact 38 of relay 39 opens the locking circuit of magnet 2I6, thereby releasing the switch 2I5 to its normal position. It should be noted that the roller 2 I9 and its actuating member 220, which is shown as a small'rail or bar, do not interfere with the free travel of carriage I3 to the end of its full normal movement to operate the contact I I! after the scanning of a long message.

In the preceding description of the operation of our system we have assumed that the doublepole switch DS at the transmitter was moved to the right for the deposit and transmission of one message. That is, after the satisfactory recording of the message, the system was shut down and the deposit chute closed. Now, by throwing the switch DS to the left, with the blades 90 and 9| engaging their respective contacts 93 and 94, the system is conditioned for continuous operation, so that a number of messages can be successively deposited and transmitted. This will be clear from the following explanation When the push button 32 at the transmitter is operated to energize the relay 33, the switch contact relay 42 is operated as before to start the transmitting mechanism, whereby a carrier current signal is generated. The recording apparatus responds to this signal as in the foregoing description and the locking solenoid at the transmitter is energized in response to the signal transmitted over the line conductor L2 to the recorder. The solenoid is locked in energized condition by a circuit which extends from bus bar B through the winding of solenoid 85, the make contact 89, switch blade and contact 93, through wire 223 to bus bar A. Once this circuit is closed, it cannot be opened by the operation of any of the relays as in the previous case. Consequently, the switch contacts associated with relay 42 remain in operated position to maintain the transmitting apparatus in continuous operation.

The opening of chute H9 and the subsequent transmission and recording of the message are accomplished in the same manner as previously described. When the recorded message is removed from cylinder 23, the relay [M (at bottom of Fig. 2) is operated and locked, and the end-ofmessage signal I93 is energized. For this type of operation the key switch I81 may be left in its normal position, as shown, while the message is being recorded. This enables the attendant at the recorder to make a second recording of the message, or he may accept it by manipulating the switch I8! as heretofore described. When the key switch I8! at the recorder is moved to A- cept position to close the contact I95, the relay I96 is operated and locked as before to apply negative potential to line conductor L2. The polar relay I1 at the transmitter is thereby operated to close its upper contact 89 to remove the message bearing sheet I2 from cylinder I 0, whereupon the relay 96 is operated as before. The closure of make contact 224 of this relay connects the negative terminal of rectifier I29 to line conductor LI.

At the recorder, in response to this negative potential, the polar relay I32 is operated to close its contact I36. A circuit is thus completed for the operation of relay I84. The opening of break contact I83 of this relay opens the locking circuit for relays I8I and I96, which are thereby deenergized. The opening or" either of the make contacts 200 or I98 of these relays removes the negative potential from line conductor L2.

At the transmitter, in response to the removal of this negative potential, the polar relay TI is deenergized and opens its contact 80. The sheet stripping magnet 203 is thereby deenergized, the Message accepted lamp 204 is extinguished, and.

the relay 96 is released. -Thus the transmitter is U ready for further operation if the recorder is in condition to record. If a blank 25 is positioned in the recorder in readiness for mounting on cylinder 23, the relay 64 will be released and positive potential applied to line conductor L2, as previously explained.

At the transmitter this positive potential produces a response by a polar relay 11 whereby the chute closure I I8 is withdrawn to make the chute III accessible for the insertion of another copy. The apparatus remains in this condition until the next sheet is deposited in the transmitter chute, after which the operation of the apparatus is resumed in the manner described.

At the recorder the attendant may place the key switch I81 permanently in Accept position to maintain the contact I95 closed at all times. In this case, as soon as the sheet bearing the recorded matter has been removed from cylinder 23 to permit the release of relay I49, the relays I8| and I96 are energized and locked simultaneously, whereupon negative potential is applied to line conductor L2.

The sequence of operation at the transmitter in response to this negative potential is identical with that previously described and results in the application of negative potential to line conductor LI. At the recorder this effects the release of relays I8I and I96, thereby restoring the recording apparatus to a condition for making another recording.

It will be noted that with the key switch I81 locked in the Accept position it is not possible to obtain a second recording of the same message. The transmitting and recording machines will operate through their described cycles as long as additional copies are inserted in the transmitter chute I I I.

The system is shut down by the opening of switch DS at the transmitter. This operation opens the locking circuit of solenoid B and permits the opening of the switch contacts associated with relay 42, thereby disconnecting the source of power from the transmitter. The absence of carrier current from the line conductors LI and L2 results in the disconnection of the re corder from its source of power, as previously pointed out.

In tracing the circuits we have used the convenicnt term wire to indicate any-practical kind or form of electrical connection. The operative connections between the transmitting station of Fig. l and the recording station of Fig. 2, represented in the drawings by line conductors LI and L2, need not be limited in all cases to metal conductors, for the facsimile impulses can be transmitted to the receiving station by radio waves.

It will be understood that the drawings which we have described in detail represent a typical embodiment of our invention and are not intended as a restriction thereof. Obviously it is not necessary that all the novel features of our invention be included in the same embodiment thereof, for certain features may be used without others. Various modifications are possible within the scope of our invention as defined in the appended claims.

We claim as our invention:

1. A facsimile system comprising a transmitter and a recorder adapted to be operatively connected for recording a transmitted message, said transmitter having scanning mechanism and means for supporting a message in scanning position, a switch operabl at the recorder after the recording of a message for sending a signal to the transmitter, a device at the transmitter energized by said signal, and apparatus controlled by said energized device for operating the transmitter scanning mechanism to scan the same mes-- sage again, whereby the recorder makes another copy of said message.

2. In a facsimile system, a transmitter having means for supporting a subject sheet in operative position, a recorder operatively connected with said transmitter for recording the transmitted subject matter, and selectively controlled means at the recorder for releasing the sheet from the transmitter after a recording thereof or maintaining the sheet in operative position therein for recording additional copies.

3. In a facsimile system, a transmitter and a recorder arranged to be operatively connected, respective sources of power for said transmitter and recorder, means at the recorder operative as a supervisory signal after the completion of a recording operation, and means at the transmitter responsive to the operation of said signal for arm tomatically disconnecting the transmitter from its source of power. 7

4. In a facsimile system, a transmitter provided with an operative member which has a normal length of movement, switch means operable by said member upon completion of its movement, other switch means operable by said member at a predetermined point before it reaches the end of its movement, a signal circuit controlled by any one of said switch means, and manually operable means for selecting any one of said switch means to energize said signal circuit.

5. A facsimile system comprising a transmitter and a recorderv adapted to be operatively connected, optical scanning mechanism in said transmitter adapted to generate a steady tone before scanning of copy, a magnet at the recorder energized by said steady tone, and a motor at the recorder automatically energized in response to the energizing of said magnet, whereby the deenergizing of the magnet automatically stops the motor.

6. A facsimile system comprising a transmitter and a recorder adapted to be operatively connected, scanning mechanism in said transmitter adapted to generate a phasing signal before scanning of copy, a cylinder in said recorder for supporting a blank in recording position, and a magnetic device in the recorder energized in response to said phasing signal for mounting a blank on said cylinder.

'7. In a facsimile system, a transmitter and a recorder operatively connected, said recorder having mechanism for mounting a blank in recording position, and means controlled by the transmitter for automatically conditioning the recorder to record the transmitted copy, said conditioning means including a photoelectric element at the recorder for controlling the operation of said mechanism.

8. In a facsimile system, a transmitter having scanning mechanism for copy to be transmitted, means for operating said scanning mechanism, a recorder having mechanism for recording the transmitted copy, said recording mechanism including an electric motor, means at the recorder responsive to the operation of said scanning mechanism for automatically starting said recording motor and apparatus at the recorder responsive to the operation of the transmitter scanning mechanism for automatically placing the recording mechanism in condition for signal reception after the starting of said motor.

9. In a facsimile system, a transmitter having scanning mechanism and means for energizing said mechanism to generate signal impulses in accordance with scanned copy, a recorder operatively connected with said transmitter and hav ing recording mechanism which includes an electric stylus adapted to remain in steady contact with an electrosensitive blank during a recording operation, connections for including said stylus in a recording circuit energized by said signal impulses, means for normally holding said stylus out of recording position, and means responsive to the operation of said scanning mechanism for automatically moving said stylus into contact with said blank and holding it steady in said contact position during a recording cycle.

10. In a facsimile system, a transmitter and a recorder having each a source of power from which they are normally disconnected, scanning iii mechanism in said transmitter and recording mechanism in said recorder means at the transmitter for connecting it to its source of power, means at the recorder activated by the transmitter scanning mechanism for automatically connecting the recording mechanism to its source of power, means at the recorder operable after a scanning operation for sending a direct current potential to the transmitter, and means at the transmitter responsive to said potential for disconnecting the transmitter from its source of power.

11. In a facsimile system, a transmitter and a recorder operatively connected, mechanism in said transmitter for generating current impulses prior to transmission of copy, a switch in the energizing circuit of said mechanism, an electromagnet at the transmitter for controlling said switch, means at the recorder responsive to said impulses for automatically starting the operation of said recorder, means controllable at the recorder for operating said electromagnet to open said switch and stop the transmitter, and means at the recorder responsive to the stopping of the transmitter for stopping the recorder.

12. In a facsimile system, a transmitter having scanning mechanism for copy to be transmitted, means at the transmitter for energizing said scanning mechanism to generate a carrier current of predetermined frequency, a recorder provided with mechanism for recording the transmitted copy, an electric motor for said recording mechanism, a local commercial source of power for said motor, means at the recorder responsive to said carrier current for automatically connecting said motor to said local source of power before scanning of said copy, and means for automatically disconnecting the motor from said local source of power at the close of a recording operation.

13. In a facsimile system, a transmitter and a recorder adapted to be operatively connected, said transmitter having a rotary cylinder adapted to support a sheet in scanning position, a normally closed chute at the transmitter for depositing sheets to be mounted on said cylinder, means responsive to an operative condition of the recorder for opening said chute, and means responsive to the presence of a deposited sheet on said cylinder for closing the chute.

14. In a facsimile system, a transmitter and a recorder operatively connected, said recorder having a rotary cylinder for supporting a blank in recording position and a stylus for recording on the supported blank, an electromagnetic device at the recorder, means at the transmitter for successively energizing and deenergizing said device before transmission of copy, means at the recorder responsive to the energized condition of said device for starting the operation of said cylinder, and means at the recorder responsive to the deenergized condition of said device for mounting a blank on said cylinder and moving the stylus into contact with the blank.

15. In a facsimile system, a transmitter having a cylinder for supporting copy in scanning position, a recorder having means for recording the copy transmitted, means at the transmitter for removing the scanned copy from said cylinder, and means controllable at the recorder for energizing said copy removing means.

16. In a facsimile system, a transmitter and a recorder operatively connected by a pair of lines, said recorder having a rotary cylinder for supporting a blank in recording position, means in said transmitter for generating carrier frequency which is sent over said lines, other means in said transmitter for imposing a direct current bias on one of said lines during the transmission of carrier frequency, and means at the recorder successively responsive to said carrier frequency and said imposed bias for automatically starting the operation of said cylinder and mounting a blank thereon.

17. In a facsimile system, a transmitter having a cylinder for holding copy in scanning position, a recorder having a cylinder for supporting a blank in recording position, means responsive to the absence of copy on said transmitting cylinder for starting the operation of said recording cylinder, and means responsive to the presence of copy on said transmitting cylinder for mounting a blank on the recording cylinder.

18. In a facsimile system, a transmitter and a recorder adapted to be operatively connected, said recorder having a recording cylinder and a motor for operating the same, a relay at said recorder, means activated by the transmitter to energize said relay and thereby energize said motor, means at the transmitter for deenergizing said relay,

17. and means at the recorder responsive to the deenergized relay for mounting a recording blank on the rotating cylinder.

, 19. In a facsimile system, a transmitter having scanning mechanism operated by an electric motor, a recorder having recording mechanism operated by an electric motor, said transmitter and recorder being operatively connected, means activated by the transmitter for energizing the recording motor, means controllable at the recorder for deenergizing the transmitting motor, and means responsive to the deenergization of the transmitting motor for deenergizing the recording motor.

.20. In a facsimile system, a transmitter having means for holding copy in scanning position, a recorder having a cylinder for supporting a blank in recording position, means responsive to the absence of copy on said holding means for generating carrier current of maximum amplitude, means responsive to the presence of copy on said holding means for generating carrier current of minimum amplitude, means at the recorder responsive to the maximum current for operating said cylinder, and means at the recorder responsive to the minimum current for mounting a blank on the recording cylinder.

21. In a facsimile system, a transmitter provided with scanning mechanism which includes a member having a predetermined length of movement from original to final position, a recorder operatively connected to said transmitter and having recording mechanism provided with means for supporting a blank in recording position, means at the recorder automatically energized when said member reaches its final position for removing the recorded blank from said supporting means, and means at the transmitter responsive to the operation of said blank removing means for causing the return of said member to original position.

22. A facsimile system having a transmitter and a recorder operatively connected, means in said transmitter for generating current impulses in accordance with transmitted subject matter, an electromagnetic device automatically energized and deenergized by said impulses during the transmission of said subject matter, a second electromagnetic device controlled by said first device and adapted to remain energized during said deenergized intervals of the first device, a driving motor for said recorder, and means whereby said motor operates only when the second device is energized so that the energizing of the second device automatically stops the motor.

23. In a facsimile system, a transmitter pro- .vided with scanning mechanism which has means for supporting copy in scanning position, a recorder adapted to be operatively connected to the transmitter and having mechanism for recording the transmitted copy, a switch at the recorder adapted to occupy two operative positions, means at the transmitter responsive to .one position of said switch for energizing said scanning mechanism to retransmit the supported copy, and means at the transmitter responsive to the other position of said switch for disconnecting the scanning mechanism from its source of power.

24. In a facsimile system, a transmitter and a recorder adapted to be operatively connected, scanning means at the transmitter for generating signal currents in accordance with the sub- Ject matter transmitted, means at the recorder for recording the transmitted subject matter, a motor for operating said recording means, a normally open switch in the motor circuit, a relay adapted when energized to hold said switch closed, an electronic device connected with said relay, and means controlled by the signal currents from the transmitter for energizing said electronic device to energize said relay, which is deenergized at the close of a transmission cycle for automatically opening the motor switch.

25. In a facsimile system, a transmitter having optical scanning mechanism for the transmission of copy to a recorder operatively connected with the transmitter, said optical scanning mechanism being adapted when energized to generate a steady tone prior to the scanning of copy, said steady tone being transmitted to the recorder which is provided with recording mechanism, a motor for operating said recording mechanism, a source of power for said motor, and a device energized by said steady tone for connecting the motor to its source of power, whereby the deenergizing of said device automatically disconnects the motor from its source of power.

26. In a facsimile system, a transmitter and a recorder adapted to be operatively connected, said transmitter having a slot for inserting copy sheets to be scanned and having a rotary cylinder for supporting an inserted sheet in scanning position, a magnet which closes said slot when deenergized, apparatus at the recorder for sending a signal to the transmitter, a device at the transmitter energized in response to said signal for energizing said magnet to open said slot and permit the insertion of a sheet for mounting on said transmitter cylinder, a switch automatically operated by a sheet on said cylinder, and a circuit controlled by the operation of said switch for releasing said magnet and closing the slot to prevent the insertion of another sheet during the presence of a sheet on said cylinder.

27. In a facsimile system, a transmitter and a recorder adapted to be operatively connected, said transmitter having optical scanning mechanism which includes a rotary cylinder for holding a sheet to be scanned, means for energizing said scanning mechanism before a sheet is mounted on said cylinder which is optically utilized to generate a carrier frequency, a local commercial source of electric power for said recorder, and switch means at the recorder ree sponsive to said carrier frequency for connecting the recorder to its local source of power.

28. In a facsimile system, a transmitter and a recorder interconnected for communication, means at said transmitter for generating a carrier current of predetermined frequency prior to a scanning operation, means at the recorder responsive to said carrier current for automatically connecting the recorder to a source of power and energizing its recording mechanism, and means for automatically signaling the energized condition of the recording mechanism to the transmitter.

29. In a facsimile system, a transmitter and a recorder adapted to be operatively connected, scanning mechanism for each of said machines, said recorder having a rotary cylinder perma nently mounted in recording position and adapted to support a blank thereon for recording, a magnet for moving a blank into position for mounting on the cylinder during rotation thereof, and a signal generated by the transmitter scanning mechanism for causing operation of said magnet.

30. In a facsimile system, a transmitter and a recorder arranged to be operatively connected, a source of power for each of said machines, a movable member for normally preventing the insertion of copy into the transmitter, means for connecting the transmitter to its source of power to generate a control signal prior to a scanning opera-tion, means at the recorder responsive to said control signal for automatically connecting the recorder to its source of power, and means responsive to the operative condition of the recorder for automatically operating said 1 3111-- be' r to permit the insertion of copy into the transmitter.

81-. In a facsimile system, a transmitter and a'reco'rder arranged to be operatively connected and having each a source of power, means whereby said transmitter and recorder are automatically disconnected from their respective sources of power after transmission and recording of each message, connections for maintaining the transmitter and recorder in continuous operation 'for repeatedly scanning the same message in the transmitter to produce a plurality of fa'csimile copies thereof in the recorder, and selectively operable means at the recorder for controlling said connections to record the desired number or copies of the same message.

-32. -In a facsimile system, a transmitter and recorder arranged to be operatively connected, said transmitter having a cylinder for supporting copy in scanning position and a slot for the in sertion of sheets to be mounted on said cylinder, means for normally closing said slot, means the transmitter for automatically conditioning the recorder to record the copy to be transmitted, means at the recorder responsive to its operative condition for sending acharacteristic signal to the transmitter, and means at the transmitter respon'sive to said signal for opening said slot whereby the transmitter is automatically conditione'd by the recorder to receive the copy to be transmitted.

33. 'In a facsimile system, a transmitter and a recorder arranged to be operatively connected,

respective sources of power for said transmitter and receiver, scanning mechanism for said transmitter having a rotary cylinder for supporting a sheet in scanning position, a device for removing a scanned sheet from said cylinder, means controllable at the recorder for causing operation of said sheet removing device, means at the transmitter automatically responsive to the removal of a sheet from said cylinder for disconnecting said scanning mechanism from its source of power, and means at the recorder responsive to the absence of a sheet on said scanning cylinder for automaticallydisconnecting the recorder from its source of power.

34. In a facsimile system, a transmitter and a with scanned subject matter, means at the 're corder i or recording said modified signal impulses,

recorder arranged to be operatively connected,

scanning mechanism in said transmitter adapted to generate unmodulated current impulses or certain frequency prior to a scanning operation, a relay at the recorder responsive to said unmodulated impulses for connecting the recorder to a source of power, said scanning mechanism causing said impulses to be modified in accordance and means for maintaining said relay energized during the absence of impulses for less-thana'pre; scribed maximum interval, said last mentioned means including a vacuum tube adapted to act as a timing device for said relay.

35. In a facsimile system, a transmitter having optical scanning mechanism which includes a cylinder for holding a sheet in scanning position, a normall closed chute for guiding a deposited sheet to said cylinder for mounting thereon, a recorder arranged to be operatively connected with said transmitter, a source of power for said recorder, means for energizing said scanning mechanism while its cylinder is empty to generate a carrier frequency of maximum amplitude which is transmitted to the recorder, means at the recorder energized by said carrier frequency to connect the recorder to its source of power, and means at the transmitter automatically responsive to the operative condition of the recorder for opening said chute for the deposit of a sheet to be scanned.

36. in a facsimile system, a transmitter an'da recorder adapted to be operatively connected through a transmission channel which includes a signal inverter at the recorder, asource of power for each of said machines, mcansatthe transmitter for generating signal impulses of certain frequency and maximum amplitude prior to a scanning operation, said impulses constituting a carrier current which is modified in accordance with scanned subject matter, a signal amplifier at the recorder connected to said transmission channel in advance of and in shunt to said inverter, a relay connected to the output of said amplifier, whereby said relay is energized by signal impulses before they pass through said inverter, a switch controlled by said energized relay for connecting the recorder to its source of power, means for maintaining said power switch closed during the zero intervals of the signal frequency, and arecording circuit adapted to be energized by the inverted signals.

RALEIGH J. WISE. GARVICE H. RIDINGS. ROBERT D. PARROTT.

REFEREIICES CITED ihe following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,747,378 Kagelman et al. Feb. 18,1930 1,848,839 Ranger Mar. '8, 1932 1,993,564; llloiler et al. Mar. 5, 1935 2,046,328 Kleinschmidt et a1. July'i, 1936 2,153,574 Kleinschmidt et al. J Apr. "11, I939 2,175,388 Gurley Oct. 10, 1939 2,212,968 Finch Aug. 27, 1940 2,214,572 Bernstein Sept. 10, 1940 2,255,868 Wise Sept. 16, I941 2,255,869 Ridings "Sept-1 6, 1941 2,326,740 Artzt Aug. 17, 1943 2,334,234 Zenner Nov. 16, I948

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