US2453269A - Printing telegraph system - Google Patents

Description

Nov. 9, 1948, H. o. RUGH 2,453,269

PRINTING TELEGRAPH SYSTEM Filed May 21, 1945 v 2 Sheets-Sheet 1 EAST STATION 1 10b 'IO loo-'1' l' ai POWER RECTIFIER 80a 6e I v I 4e- 7 I 86 '|f NONLOCK TRANS KEY 5 LOCK TRANS. load PRINTER 602 TRANSMITTER 50;:

56c [13 M11 I I 8 Y Y Y FY mmn 1 I l j INVENTOR.

HARRY o. RUGH BY. OWMV\M M ATTORNEYS Nov. 9, 1948. H. o. RUGH 2,453,269

PRINTING TELEGRAPH SYSTEM Filed May 21, 1945 2 Sheets-Sheet 2 WESTYSTATION IO lob F l6. 2

' I IOCL] TRANSMITTER 50w 58w INVENTOR.

HARRY O. RUGH ATTORNEYS Patented Nov. 9, 1948 UNITED STATES ATENT OFFICE PRINTING TELEGRAPH SYSTEM Harry 0. Rugh, Chicago, Ill., assignor to Automatic Electric Laboratories, Inc., Chicago, Ill., a corporation of Delaware Application May 21, 1945, Serial No. 594,833

'7 Claims. 1

The present invention relates to printing telegraph systems and, more particularly, to improvements in the methods and apparatus for transmitting and receiving coded signals over standard commercial power lines.

In the Harry 0. Rugh Patent No. 2,290,385, granted July 1942, there is disclosed a printing telegraph ystem having a transmitting station, a receiving station, and an interconnecting line over which. coded signals are transmitted to control the receiving station printer. That patent is concerned more particularly with the mechanical structure of the sending and receiving apparatus. The present invention, however, deals with the use of the mechanical transmitter and receiver apparatus disclosed in the above-mentioned patent in a system in which a commercial power line is utilized as a carrier channel in the transmission and reception of signals in either direction.

It is an object of the present invention to provide in a system of the character described an improved transmitting unit for producing carrier current having a frequency of oscillation above the audible range and modulating such oscillations, means of an audio frequency oscillator and a sender, in accordance with a telegraphic code.

It is another object of the invention to provide in a system of the character described an improved receiving unit for receiving and demodulating the received modulated carrier wave in order to control a printer unit in accordance with the received signals.

It is a further object of the present invention to provide in a system of the character described a combined transmittin and receiving unit whereby the apparatus, provided at any one of the stations of the system, may be utilized either as a transmitter or as a receiver.

is a still further object to provide an economical and ehicient arrangement for converting the combined. ansmitting and receiving unit so that it may be selectively operated as a transmitter or a receiver.

It is a still fur :ler object of the present invention to provide in a system of the character de scribed a. new and improved arrangement for scrambling the coded signals of a message as they are being tran ".iittcd and for automatically unscrambling the transmitted coded signals as they are received, wh reby the telegraphic printer at the receiving station may be operated to correctly print the coded signals of the transmitted message.

In accordance with another object of the invention different scrambling or transposing devices may be provided between the selecting bar contacts and the sending commutator of the sender at the transmitting station, whereby the transmitted code signals may be scrambled at will in accordance with difierent patterns by merely substituting different transposing devices.

In accordance with still another object of the invention different unscrambling or transposing devices may be provided between the printer control magnets and the receiving commutator at the receiving station, whereby the received scram bled code signals may be unscrambled as they are received in order to control the printer to correctly print the transmitted message.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the specification taken in connection with the accompanying drawings in which Figs. 1 and 2 illustrate the circuit arrangementof an improved system having incorporated therein the features of the invention briefly referred to above.

Referring now more particularly to Figs. 1 and 2 of the drawings, the improved system there illustrated comprises, in general, an east station (Fig. 1) and a west station (Fig. 2) which are interconnected by a commercial power line ID. The power line iii also constitutes the source oi operatin current for the stations of the system and may, for example, be of either 110 volt alternating or direct current type.

The apparatus and circuits provided at the east and west stations are identical and, accordingly, like reference numerals, distinguished only by the letters e and to, have been used to identify corresponding apparatus and circuit elements.

These stations respectively comprise sound translating devices to and 310, each of which serves as a microphone and as a loudspeaker, combined carrier current oscillator-detector networks 20c and 20w, combined audio oscillator-amplifier networks 306 and M10, power rectifier units Slle and 80w, key operated transmitter units Elle and 50w, tape printer units tile and w, and printer controller amplifier networks l'hle and 19w; For the purpose of rendering the respective stations active for either transmission or reception of voice and printing telegraph signals, switch keys 4e and 4w are provided. There are also provided at each of the stations, respectively, transmit and receive keys 5c and 5w having three positions for controllin the respective stations for transmission or reception of signals over the power line 10,

The oscillator-detector unit Zfie provided at the east station comprises a vacuum tube 21a of the type and construction identified commercially as the type 25A6, inductance coils 22c and 23e which are inductively coupled to a pickup inductance coil E ie, a variable tuning condenser 25c, a blocking condenser 26c having a low impedance to carrier frequencies and a high impedance 'to audio frequencies, and a grid biasing network including the resistor 2'ie shunted by, a by-pass condenser 28c for maintaining correct operating potential upon the control grid ofthc vacuum tube 2 le. In this unit the condenser 25c and the inductances 22c and 23e comprise'acircuit electrically tuned to give oscillations of the desired frequency of, for example, 60 kilocycles.

Since the oscillator-detector 28c when operating.

as an oscillator functions in substantially the same manner as is described in the Hartley Patent No. 1,356,763 granted October 26, 1920, and

is-we'li known in the art, it is not deemed necessary to again describe the detailed operation thereof. 7

Theamplifier 38c provided at the east station comprises the amplifying stages 3 l e and 32e which respectively includevacuum tubes 33c and 34e. The amplifier tube 33s is of the commercial 6J7 pentode type and includes input electrodes 35c and 36a, the former electrode being connected to the shielded conductor 31c, and output electrodes fier of the commercial 25N6 type having one triode, the driver, directly connected to the second, or output, triode. The input triode plate electrode tile of the tube 34c is connected to the conductor i'le extending to the power rectifier unit Bile and to one terminal of the primary winding of the output transformer ite. The output triode plate electrode ite of the tube 3% is connected to the other terminal of the primary windin'gof the transformer 68c and to the conductor 49c, and is icy-passed for high audio frequencies by a condenser Me.

Forth'e purpose of supplying positive screen and anode potentials to the screen and anode electrodes of the tubes Zie, 33c and Me, a powerrectifier, indicated at 88c, is provided. This rectifier comprises a half-wave, high-vacuum rectifying tube 81c which is commercially known as the 2526 type and is designed to supply direct current power from an alternating or direct current power line. lVl'o-re specifically, the ungrounded conductor idol of the power line Wis connected by way of the blocking radio frequency choke coil 82c to the plate electrodes of the tube 81c, and, in multiple therewith, is serially connected by way of the filaments of the tube 816, the ballast resistor 83c which is partially shunted by a signal lamp Me, the two filaments of the tube Me in parallel, the filament of the tube 216, and the filament of the tube 33c, to the grounded conductor Ific of the power line 15 by way of'the contacts of the switch key ie. It should be understood that the ground symbols indicated on the drawings merely indicate that such connections are soldered to the chassis mounting the apparatus disclosed, and the circuits including these grounded symbols are not completed until the switch key to is actuated to connect the chassis to the grounded conductor Jill) of the power line Iii. Accordingly, the above traced circuit provides the necessary current supply for the filaments of the various tubes provided at the east station.

The cathodes of the rectifier tube Ble are connected in multiple, through a filter network 85c which" includes a series connected iron core choke coil 86c and a pair of shunt connected filter condensers BJe'an'd see, to the conductor 41a. The

, conductorile is connected directly to the plate electrode are of the driver section of the amplifier tube 34c and isalso connected to the output triode plate electrode We of this tube through the prima'ry'winding of theoutput transformer 48c. Similarly, the required positive potential is impressed'upon the anode electrode 38of-'-the*ampl-ifi'er' tube 33c through the plate load resistor" This circuit is also provided with a consea denser'fii'e for lay-passing carrier-currents which might appear across-"the output of thetube' 336;

Positive operating potential is supplied to the screen-electrode of t-he'amplifi'er tube are through" the current limiting resistor Me which by-' passed -fo'r alternating currents by a condenser 91c.

The-secondary windin'g'of the output transformer 48c is connected by way of the normally closed contacts l-ilii-e of the key Eetothe sound translating device 3e, so that voice receptionmay" 1 be-utilized'in a; manner to'be described herein: It-should also benoted that the jack 92a: andthe' plug SIie-are provided to interconnect'th'e' tape printer unit We and the schematically illus' after.

trated' amplifier unit we inseries with the sec ".3 ondary winding of the output transformerifie Withthis, arrangement the'eaststation tape printer Bile. maybe controlled-to record messages transmitted" over the power line lll by the west'st'a'tion, in a" and the sound translating device 3e.

manner to-be described hereinafter:

-Referring now to the telegraph transmitter unit 58c, attention is" directed to the fact"that this unit is disclosed in detail in the above-men tion'ed Rugh" patent. transmitter"comprises a plurality of keys E'i'e'arrangedto be actuated by'an operator to complete circuitsthrough the select bars are (I-V) in' accordance with a prearrangedcodei When a key, such as He, is actuated, certain ofith'eselect bars 524; (I"V) are energized'an'd, at the same time'the insulated trip leverv53'c is rotated slightly in a clockwise direction and withdrawsthecatch memberfifl'e from thedistributor arm 55c. When this occurs the distributor arm 55c is driven a single revolution in'the'direction indicated,.by. a ni'otornot shown, over the contacts 56e"(I'V), certain'ones of which are marked bythe actuated key t le and the associated select bars 52a. in accordance with the code ofa vparticular letter or digitlto-be transmitted. Itwill benotedthat' when the distribut'orarm 55c rotates a slight distance, it engages the start contact He thereby.

to complete a circuit including the control con- Briefly considered, the.

kilocycle carrier wave generated by the oscillator Zlle in accordance with the particular code of the letter or digit to be transmitted. A detachable transposing plug 596 is also provided in order to scramble the signals of the prearranged code of each of the operated keys 54c. Referring to the drawings, it will be noted that the A111 terminal of the plug 596 is connected to the EV terminal thereof, and that the AIV and AV terminals are connected, respectively, to the B111 and BIV terminals. It will be understood that many other combinations may be utilized to scramble th coded signals by interchanging dif ferently jumpered detachable transposing plugs, such as 596, in the circuit extending between the select bars 522 (IV) and the contacts 56c (I-V).

The east station may be coupled to the power line I8 by way of an inductance-capacitance network 6e, comprising the indu-ctances 1e and 8e and the condensers I he and I26, and the variable coupling condenser Be, one branch of this circuit extending by way of the variable volume control 53c and the other branch extending by way of the contacts Ellie or 35c of the key 52 to the pickup coil Me of the oscillator-detector unit 22c.

In considering the operation of the system, it may be assumed that the operator at the east station has actuated the key ie, thereby to condition the oscillator 206, the amplifier 30c, and the power rectifier 8536 for operation. It will also be assumed that the operator has actuated the key 56 to its locking transmit position, thereby to close the contacts m le, 35c, [61c and Hide and to open the contacts H336 and I052. As a result of the actuation of thekey ie the signal lamp Me is illuminated to indicate to the operator that the circuits at the east station are in condition for either transmission or reception of coded signals. As a further result of the actuation of the key ie the previously traced filament circuit is completed for the tubes He, 33:: and 346 and the power rectifier functions to sup ply the necessary positive operating voltage to the screen and anode electrodes of the tubes 33c and 342.

When the contacts [846 are closed, as a result of the actuation of the key So to its locking transrnit position. the positive voltage which is applied to the conductor Me by the power rectifier 80c and extending by way of the primary winding of the output transformer ice to the plate electrode ite of the tube 342. is now further extended by way of the conductor 696, the contacts lll le and the inductance 23c to the screen grid and plate electrode of the tube 21c. The oscillator Zfle now oscillates at a frequency which is dependent upon the values of the condenser 25c and the inductances 22c and 236. t will be assumed that the circuit values are such that the oscillator produces a carrier wave having a frequency of 60 kilocycles per second. Accordingly, the carrier wave is transmitted over the power line It: by way of the inductively coupled pickup coil Me, the contacts I856, the variable condenser Se, and the network fie.

As a further result of the actuation of the key e at the contacts 1616 a circuit is completed for connecting the translating device 3e to the seconclary Winding lEie of the transformer lfie. At the contacts I935 a circuit is also completed from ground by way of the primary winding We of the transformer lee which is shunted by the resistance I86, the contacts [086, and the shielded conductor 31a to the control grid 35c of the first amplifier tube 336.

With the system in the condition described above, if the operator at the east station speaks into the translating device 36, a signal voltage is developed across the low impedance primary winding l5c of the coupling transformer I66. This voltage is reproduced across the secondary winding l'le of the coupling transformer lfie and is impressed between the input electrodes 35c and 36e of the first amplifier tube 336. When amplified by the tube 336, the signal voltage is impressed through the resistance-capacitance coupling network to the input control grid of the tube 34c. When amplified by the twin triode direct-coupled power amplifier tube Me the signal voltage is impressed by way of the conductor 49c, the contacts Me and the inductance 23a to the screen grid and plate electrodes of the tube 2le. 'Ihe audio signal voltage impressed in this circuit modulates the carrier signal produced by the oscillator Zlle. The modulated carrier signal is now induced into the pickup inductance coil 24c and transmitted over the power line H] to the west station where the signal is demodulated and reproduced by the translating device 310 as will be subsequently described in connection with the operation of the east station.

From the foregoing description of the operation of the apparatus and circuits at the east station, it will be understood that the carrier wave produced by the oscillator 2Ele is modulated in accordance with the audio signals produced by the translating device 3e and amplified by the amplifier 30c.

Referring again to the circuit for impressing the positive operating potential upon the conductor 496, it will be noted that in addition to extending to the anode and screen grid elec trodes of the oscillator tube Zle, this circuit also extends by way of the conductor 586 to the distributor arm 55a of the transmitter lice. Furthermore, the key Me is connected by way of the conductor 51c, the condenser Hie and the shielded conductor 37a to the control grid 356 of the amplifier tube 33c. Accordingly, it will be understood that when a circuit is completed between the conductors 51c and title as a result of the actuation of the key 556 of the transmitter 50s, the output of the amplifier 386 is thereby coupled to the input of the amplifier 30c to complete a regenerative connection for the amplifier 396. This regenerative circuit causes the amplifier to act as an audio frequency oscillator whose output appears across the primary winding of the transformer 386. Since the secondary winding of the transformer Me is open the primary Winding acts as a plate load impedance for the output section of the tube 342. Attention is directed to the fact that the impedance of the primary winding of the transformer 48c is common to the output section of the tube 34c and to the plate supply circuit for the carrier oscillator 20c and thereby causes modulation of the carrier wave, at the audio frequency of the amplifier 306. The frequency of oscillation of the amplifier the, when it operates as an oscillator, is determined by the circuit constants of the elements included in the amplifier 306. It will be assumed that these constants are such that the amplifier 30c oscillates at an audio frequency of 400 cycles per second. It should also be understood that the audio voltage superim posed upon the positive voltage applied to the conductor 49:: causes the carrier wave produced by'the oscillator tube 21a to be'amplitude-modulated at four hundred cycles per second.

From the foregoing descriptionv it should. be

understood that each time a key,'.such as tile; is" actuated by the operator, the distributor" arm 55c makes one complete revolution and,.depend.-

ing upon the markings on theasso'ciated contacts- BSe by the particular selectbars-52e,.the-amplifier 386 is controlled over the conductors 51c and 58a to oscillate in the above described manner.

Accordingly, the steady 60 kilocyclecarrier'wave transmitted by the oscillator Zile'may'b'e modulated by the 400 cycle audio frequency of theamplifier 3536 each time the distributor arm 55c engages the start contact '1 le or a contact marked by the select bars 52c.

When the operator at the east station has completed transmission of the'desired messageby the manipulation of the keys Me of the transmitter 53c, the three-way key e'ma 'be'restored to its neutral orreceive position. Accordingly, when the contacts tilde are opened the positivepotential applied to the conductor 496 is disconnected from the oscillator e,.and,.when the contacts I 956 are opened the volume. control 136 is in-- cluded between the pickup coil 24c of the-oscil at the contacts mile, thesecondary. winding. lle:

of the transformer lfie is disconnected from the control grid electrode 356.

When the contacts lllfie'of the key 5c are closed,

a circuit is completed for extendingthe' positive. voltage applied to the conductor Me by. way-of the resistor 29c, the contacts Be, and the in ductance 23c to the plate and screen grid electrodes of the oscillator tube Me. The plate voltage of the tube 21c has now been reduced substantially by the resistance 29e included in this circuit and prevents the oscillator 20c from oscillating in the previously described manner. Ac cordingly, the tube Zle will now function as a detector in order to detect modulated carrier waves transmitted over the power. line it) by. another station of the system. At the: contacts lillie, a circuit is completed for connecting. the sound translating device 3e to the secondary. winding of the outputtransformer 486 of the amplifier 36c, whereby voice signals transmitted over the power line may be reproduced by the translating device 3e.

In order to describe the operation of the system when the key 5c is in its neutralposition, it will be assumed that a 60 kilocycle carrier Wave is transmitted by the west station of Fig. 2, and it will further be assumed that the carrier signal is modulated by the sound translating, device 3w in accordance with sound waves received thereby. Accordingly, this modulated carrier waveisreceived at the east station of Fig. 1 by way. of the network 66, the variable condenser fie, the volume control lite, and the pickup coil 24a, Thissignal is detected by the tube 2|e due to the inductive coupling of the inductance windings 24c and He. The modulation components of the received signals are detected by the tube Zle and appear across the plate load resistor 29c. The audio-volt.- ages developed thereacross are impressed upon the control grid electrode 356 of the amplifier 306 over a circuit which includes the condenser I96 and the shielded conductor 31c. Theaudiosignal components of the modulatedv carrier signal are thus impressed upon the abovetraced-circuit: and

At the contacts lllle,.the' sound trans ar'e' ampllfie'd in thefpreviously described manner wave will be reproduced by the sound translating.

device' 36 at the east substation.

If the subscriber at the east station desires to receive printing telegraph signals transmitted overthe power line I 0, the plug 93e is inserted into the jack 92c thereby to connect the schematically illustrated amplifier" llle in serieswith the sound translating device 3e. Attention is directed to the fact that theprimary winding of the input: transformer of the amplifier lfieshouldbe' substantially equal to the impedance. of-the-sound translating device file-in order thatthesignabre ceived in the secondary winding of the output transformer 486 may be reproduced with equal amplitude by the sound translating device 32 and the input transformer of the amplifier rectifler Hie.

It will now be assumed that the operator at-the west station'cf Fig. 2 hasmanipulated the keys of the transmitter 59w to transmit printing telegraph signals over the power line It in substantially the same manner as has been described. in connection with the operation of the transmitter Eille at the east station. When such signals are received at the east station-the tube 2 le functions to detect the signals and the amplifier 36c functions to amplify the signals, ashas been described above. The signals .amplifiedrin the above manner are further amplified by the amplifier llle which also rectifi'es the signals to controlthe operation and release of the relay file of theprinter 806 in accordance with the coded signals. It will be recalled that a start signal. is transmitted by the transmitter each time the distributor arm 55e or 55w is moved oil normal. This signal precedes the signals transmitted in accordance with the coded signals of the letter and causes therelay file to operate and withdraw the catch member 826 from the distributor arm 63c. The arm 63a is fricticnally engaging. a continuously.- rotating shaft and starts rotating in the indicated direction as soon as the catch memberv 626 is withdrawn. When the arm 63c engages the contacts E ie (I) the relay. elemay. or may not be operated, depending upon the code pulses of the letter or digit being transmitted by the operator at the west station. It will be assumed, however, that when the arm tile is in engagement with the contact 64c (I), the arm 5520 is also in engagement with the contact Eitw (I) at the transmitter 50w, and that this contact is marked by. the key 5lw. Accordingly, the carrier wave received at the east station will be moduiated' by the 400 cycle audio frequency to cause the relay File t reoperate. Upon reoperating; the catch member 62c actuates the contacts 65c to complete a. circuit which may be traced from battery, by. way of the contacts title, the arm 83c, the contacts Me (I), the BI and the AI terminals of the transposing plug 6%, andtherelay 666. (I) to ground. From the foregoing description-it should be understood that as the arm 55w of thetransmitter Eilwrotatesover thesuccessive contactstfiw (IV-). thearm 63c of thepointer lille will successivelyengage thecorresponding contact lite (IV) in synchronism therewith. Accordingly, the relays 66e(IV')- are operated in combinations depending upon the a single revolution of the arm 63c, the printer i 60c is controlled in the manner described in detail in the above mentioned Rugh patent to print the letter or digit corresponding to the particular key actuated at the transmitter 50w.

After the operator at the east station has received the complete message transmitted by the operator at the west station, the operator thereat may desire to signal the operator at the west station to indicate that he desires to answer the message transmitted therefrom. In order for the operator at the east station to transmit an attention signal, the key 56 may be momentarily actuated to its non-locking transmit position. When the key 5e is actuated to this position, the contacts I [lie are closed to connect the pickup coil Me to the power line l over a circuit which is independent of the volume control l3e. When the contacts I 02c are closed the positive potential applied to the conductor 496 is connected by way of the inductance 23c to the plate and screen grid electrodes of the tube Zle. Attention is directed to the fact that this circuit is substantially the same as the c rcuit previously traced, including the contacts "Me of the key e, and, accordingly, the oscillator 20c functions in the previously described manner to oscillate at 60 kilocycles per second. It will also be noted that the conductors 51c and 58a extending to the transmitter 50c are shunted by a circuit including the contacts [Me and |U3e of the key 56.

As a result of the above described actuation of the key 5e to its non-locking transmit position, a regenerative connection is completed from the output electrodes of the tube 34c by way of the conductor #96, the contacts H126 and I032, the condenser Ne, and the shielded conductor 37c to the control grid electrode 35c of the amplifier tube 33c. When this regenerative connection is completed the aud o amplifier 30c acts as an audio frequency oscillator and oscillates at approximately 400 cycles per second. The 400 cycle audio frequency generated by the amplifier 30c modulates the 60 kilocycle carrier wave generated by the oscillator 28c, and is transmitted in the previously described manner over the power line I0.

Any other station of the system having its key, 7

such as the key 5e, in its neutral or receive posi tion will function in the manner previously described to control the sound translating device thereat to produce a 400 cycle tone signal. This signal will indicate to the operator thereat that.

another operator of the system is about to transmit printing telegraph coded signals.

In order to describe the manner, in which the coded signals are scrambled during the operation of the transmitter 50c, it will be assumed that when the key 512 of the letter C is actuated, the code select bars 52c (II, III and IV) are marked to transmit the code signals of the letter,

C. Consequently, when the arm 55c rotates in the direction indicated the contacts 56c (I and IV) are unmarked and the contacts 56c (II, III and V) are marked, due to the cross connections of the transposing plug 59c. As a resultof the above described markings placed upon the contacts 56c of the transmitter 50c, the apparatus at the east station is controlled to transmit a carrier signal of 60 kilocycles which is modulated by a 400 cycle audio frequency at spaced intervals in accordance with the coded signals controlled by 10 the above mentioned marked contacts 566 (II, III and V). When these signals are received by the apparatus at the west station, the relay Glw thereat controls its associated contacts 6520 to successively energize the contacts 642:; (II, III and V). Thus, when the contact 6520 (II) is energized, a circuit is completed by way of the BII terminal of the transposing plug 5%.: and the AII terminal thereof for energizing the relay 65w When the (i420 (III) (II) of the printer 68w. terminal is energized, a circuit is completed by Way of the BIII terminal of the transposing plug 6520 and the BIV terminal thereof for energizing the relay 66w (IV). When the terminal 6410 (V) is energized, a circuit is completed by way of the EV terminal of the transposing plug 69w and the A111 terminal thereof for energizing the relay 66w (III). As a result of the energization of the relays 66w (II, III and IV) the letter C is printed by the printer It will be understood from the foregoing description of operation of the printer apparatus at the west station that if the transposing plug 6910 had not been wired in the same manner as the transposing plug Me at the east station, and had been wired straight, then the relays 6620 (II, III and V) would have been energized to print a letter other than the letter C, for example the letter P. Since any number of transpositions may be made by providing a plurality of transposing plugs, each wired in a diiIerent manner, it

will be understood that a transmitting station of the message, the printing apparatus at such stations will print a message which is undecipherable by the operator thereat, but at the receiving station Which has the proper transposing plug connected to the printer apparatus, that is, a transposing plug corresponding in wiring to the transposing plug utilized by the transmitting station, the message recorded by the printer thereat will have been deciphered and correctly printed to correspond with the message transmitted.

While one embodiment of the invention has been disclosed, it will be understood that various modifications may be made therein which are within the true spirit and scope of the invention.

What is claimed is:

,1. In combination with a printing telegraph station having a transmitter for transmitting a message by telegraphic coded signals and a receiver for printing a message transmitted by telegraphic coded signals from, another s,tation,'"a

unitfadapted tobe. operated as a carrier current oscillator or as a detector, means at. said station tion thereby to control said unit to detect the audio portion of a telegraphically coded modulated carrier wave received at said station.

2. In combination with a printing telegraph station having a transmitter for transmitting a message by' telegraphic coded signals and a retector, means :at said-stationfor applyinga-predetermined positive voltage to said unit when saidstation is to be-operated'as aitransmittins -station thereby to control said'unit to transmit :a superaudio carrier frequency, means .at said stationdor modulating said carrier frequency?:

with an audio frequency in accordance :With a :tclegrapl'iic code to'transmit a message, means'at sai'dnstation for applying a predetermined lesser positivevoltage t0=said unit when-said station "is' tobe operated as a-receiving station thereby to control said unit to detect-the audioportion of 1a telegraphically coded-modulated carrier wavere- :ceived.at said station, and means controlled accordance with said detected signals for controlling said printer to make a record ofthe received message 3. lIn-a communication system, a line,:a'stati-on connected to saiddine, sai'd station comprising a first combination "carrier current oscillator and detector device, a second combination audio ire "quency oscillator and amplifying .device, a key controlled transmitter, and a printer; control 'meansat said'station actuated in one manner when said station is-operated as a transmitting station for altering'saidfirst device-to cause'itto --operate as a carrier current oscillator thereby to transmit carrier current oscillation-s over said "line, means controlled by said transmitter *for causing said-second device tooperat'e-as an-audio frequency oscillator-thereby to modulate said-carrier current oscillations in -accor'dance witha telegraphic code, said control'means actuatedin another manner wh-en'said station isoperated as a receiving -station f or altering said first device to cause'itto operate as a detector therebyto demodulate received "modulated carrier current 1 0-5-- *ci'llations and for causing said second device to operate as an amplifier thereby to amplify the "said 'dem odula-ted -,oscillations, and means con- ,trolledby said second "device when operated as-an amplifier ;for 'zcontrolling said printer ,to "p oduc arecordof 'the" letters or digitsrepresented by the received demodulatedoscillations.

4. In-combinationwith aprinting telegraph sta- 'tionihaving a transmitter-for transmittingames- '1 sage by telegraphic coded signals and a receiver for printin-ga message transmittedby telegraphic coded signals from another station, a carrier current oscillator, a combination audio fre uency os'cillator'and amplifying device, a key controlled transmitter, a printer, a con-troljkcyyat said station actuatedin one manner'whensai'd stationis .oncrate'dasa transmitting station for activating said carrier current oscillator to transmit Jacarrier wave, means controlled by .said transmitter for causingsaid device'tooperate-as an audio-frequency oscillator'thereby to modulatesaid carrier wavejnaccordance withatelegraphic code, said .control'kcy aotuatedin anothermanner when said stationlis operated asareceiving stationgfor alteringsaid carriercurrent oscillator to cause it to onerate ,as aldetector .to demodulate received .mod- .ulated carrier waves andnfor. altering said device tocauSe i it ,to operate as. an amplifier thereby to -.ampliy :said demodulated carrier .waves,

means controlled. byz-said device when o eratedas an amplifier for controlling said printer toy pro- .duce la .record ofthe letters, ordigits-represented .bythe :received demodulated carrier ,waves.

5.5.;Incombinationwithaprintinatele raph sta- -"tion' having a transmitter for transmitting a mes-' sageby telegraphic coded signals and a receiver "forprinting -a message transmitted by telegraphic coded signals-over another station, a sound translating device,-a unit adapted to be operated asa carrier current oscillator or a detector, means at said station for applying a predetermined positive voltage to saidnnit when said station is to be operated as atransmitting station thereby to control said unit to transmit a superaudio carrierfreyquency, m,eans at said station for modulating-said carrier frequency with an audio frequency inac- -cordanoe *with a telegraphic code to transmit a message,'said last-mentioned means also control- 'l-ablebysaid sound translating device for modulating said carrier frequency with an audio frequency in accordance with sound waves received by saidsound translating device, means at said stationdor applying a predetermined lesser positive voltageto said unit when said station is to be operated as;a receiving station thereby to control gsaid unit to detectthe audio portion of a modulated carrier wave received at said station, said amplifier amplifying said detected audio portion ;;of a modulated carrier wave thereby to control said sound'translating device-to reproduce sound --waves-in'accordance therewith and'to cause said "receiver'to print a messagein accordance with the audio portion of a ,tel-egraphically coded modu- "lated carrier Wave.

In combination with ,aprinting telegraph station having atransrnitter for transmittinga -message by telegraphic coded signals and a receiver 'ior'printlng'a mess-age transinittedby telegraphic coded signals from another station, a soundtranslating device, a first unit adapted to lie-operated asa carrier current oscillator or as a detector, a second unit including an input and an 'outputcircuit adapted to be o;;:erated as an audio "frequency oscillator ,or as an amplifier, a switching keyadapted to be actuated in a first manner 'to'condition said station to be operated as a transmitting station andadaptecl to beoperated in a secondmanner. to condition said station to be .01 eratedgas a receiving station, contacts controlled said key when actuated in said first mannerior controlling said first unit to operate as a carrier current oscillator to generate a carrier wave and for connecting said sound translating device to said input circuit whereby said second unit operates as .an amplifier, means including said output circuit for modulating said carrier wave with amplified audio frequencies in accordance with sound waves received by said sound translating device and transmittedover said input circuit, means incl-udingthc transmitter at said station for intermittently connecting said output circuit and said input ,circuit of said second unit in accordance withatelegraphiccode thereby to cause said second unit to modulate said carrier wave with a telegraphically coded predetermined audio frequency, contacts controll d by said. key when actuated in saidsecond manner for controlling said first unit to operate as -a detector thereby to detect the audio :port-ion'of a-modulated carrier Wave received at saidstation and for connecting said sound translating device to said output circuit and connecting said input circuit to said detector whereby the tie tented raudio portion of said modulated carrier Wave,i-sramplifiedby said second unit and reproduced as sound waves by said sound translating device,-anfd means for coupling the receiver at said station topsaid output circuit in order to print a message Sin accordance with the detected audio 13 portion of a telegraphically coded modulated carrier wave.

7. In combination with a printing telegraph station having a transmitter for transmitting a message by telegraphic coded signals, a sound translating device, a first unit adapted to generate a carrier wave, a second unit including an input and an output circuit adapted to be operated as an audio frequency oscillator or as an amplifier, a switching key, contacts controlled by said key for controlling said first unit to generate said carrier wave and for connecting said sound translating device to said input circuit thereby to condition said second unit to operate as an amplifier, means including said output circuit for modulating said carrier wave with amplified audio frequencies in accordance with sound waves received by said device and transmitted over said input circuit, and means including the transmitter at said station for intermittently interconnecting said output and said input circuits in accordance with a telegraphic code to cause said second unit to operate as an audio frequency oscillator whereby said carrier Wave is modulated in accordance with a telegraphically coded predetermined audio frequency.

HARRY O. RUG-H.

REFERENCES CITED The following references are 01 record in the file of this patent:

UNITED STATES PATENTS

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