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Publication numberUS2491244 A
Publication typeGrant
Publication date13 Dec 1949
Filing date27 Apr 1946
Priority date27 Apr 1946
Publication numberUS 2491244 A, US 2491244A, US-A-2491244, US2491244 A, US2491244A
InventorsBecker Harry W
Original AssigneeBecker Harry W
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Signal receiving and transmitting apparatus
US 2491244 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

. 1949 H. w. BECKER 2,491,244

SIGNAL RECEIVING AND TRANSMITTING APPARATUS Filed April 27; 1946 2 Shets-Sheet 1 Dec. 13, 1949 H. WJBECKER 2,491,244

' SIGNAL RECEIVING AND TRANSMITTING APPARATUS Filed April 27, 1946 2 Sheets-Sheet 2 u l :7 E

2 m; a r

- my r29 Patented Dec. 13, 1949 UNITED STATES PATIENT OFFICE SIGNAL RECEIVING AND TRANSMITHNG APPARATUS 18 Claims.

This invention relates to signal receiving and transmitting apparatus and more particularly to the receiving of signals from and transmission of signals to a remote point without the use of a local power supply.

In my Patent No. 2,389,949 there is described and claimed an apparatus for receiving power and signals from a remote point over a single path such as a pair of wires. The present invention provides an improvement in the apparatus of the patent to permit generation and transmission as well as reception of signals.

One of the objects of the invention is to provide apparatus in which a tuned circuit may be used to select a signal to be received or to produce oscillations for transmission.

Another object is to provide apparatus which may be supplied with power from a remote point to produce signal oscillations for transmission to the remote point.

Still another object is to provide apparatus which can easily and quickly be switched to act as either a receiver or transmitter.

The above and other objects and advantages of the invention will be more readily apparent from the following description when read in connection with the accompanying drawing, in

which- Figure 1 is a circuit diagram of one form of apparatus embodying the invention; and

Figures 2 and 3 are circuit diagrams of'al'ternative constructions.

The apparatus of Figure l is substantially identical with that of my Patent No. 2,389,949 with the exception that switches and other circuit components have been added to enable it to function as both a receiver and a transmitter. As shown the apparatus is adapted to receive any selected one of five signals transmitted over a supply circuit formed by a pair of wires I and II which may connect terminals on the apparatus to a remote point. The apparatus may also generate signals at any one of five selected frequencies which may be transmitted over the circuit Ill-II to the remote point. As described herein, the signals may be audible signals such as voice or music, although it will be apparent that any other desired type of signals could be received or transmitted. The wires Ill-I I are connected to a source of heating current and .to a

source of direct current, the heating current being at a supersonic frequency in case the signals are in the audible range. When the apparatus is to be used as a receiver, the wires In and Il may also supply five carrier currents of different frequency modulated by the audible signal frequencies, the carrier currents bein in each case at a frequency diflferen't than that of the heating current.

The apparatus comprises an electron discharge tube shown as a tetrode having a filament type cathode I2, a control grid I3, a screen grid I4 and a plate I5. The supply line IIJ is connected through a .resonant circuit including a coil I6 in series with a second coil I! which is in parallel with a condenser I8. The condenser I8 and the coil H are connected through a line I9 and a bypass condenser 2| to the line II. The resonant circuit I6--I8 is tuned to offer a minimum impedance to the heating current but substantially to block the carrier frequencies.

The coil I'I serves as the primary of a transformer whose secondary 22 is connected across the filament I2. The transformer blocks the direct current so that the filament is directly heated by the high frequency heating current.

The plate I5 of the tube is connected through a plate load resistor 23 to the line I9. The direct voltage in the supply circuit will therefore be impressed on the plate across the load resistor, the alternating currents being bypassed back to the supply 'line'through the condenser 2| The screen grid |4is also connected to the line I9 through a dropping resistor 24 and is bypassed to the'sllpply line through a condenser 25 to eliminate any alternatin components.

The output signal is reproduced through a speaker or headset 26 which is connected to the supply line II and which may be connected to the plate l5 through a blocking condenser 21. While the signal reproducing device has been shown as a headset for reproducing audible signals, it will be understood that it could be any other desired type of signal reproducer and that it could be connected to the tube through one or more amplifier stages, if desired.

The signal currents are conducted from the.

wire II! through a blocking condenser 28 to eliminate direct current to a coil 29 which is grounded at 30., Since the wire II is grounded as illustrated at 3|, the coil 29 is connected across the supply line. The coil 29 may be tuned to resonance with any one of the several carrier vfrequencies by connectin in parallel therewith one of five condensers 32. For this purpose the condensers are connected to separate contacts which may be selectively engaged by a switch .arm 33 connected .to one side of the coil .29. The other sides of the condensers may be grounded .at 3.4. The condensers may be adjusted to tune the circuit to the selected frequency so that any one of the five carrier frequencies sup-plied over the wires I t and I I may be selected for reproduction. In will be understood that if desired a single variable condenser could be employed to tune the circuit to any selected frequency within the operating range of the apparatus. The coil 29 is connected to the control grid I3 of the tube through a coil 35 which is loosely coupled to the coil 29. The coil 35 is connected at one end to the grid l3 and at its other end to the filament I2 through a grid bias resistor 36 bypassed by a condenser 31. The coil 35 may also be tuned to any one of the signal carrier frequencies by connecting in parallel therewith any selected one of five condensers 36 by means of a switch arm 39. Preferably the arms 33 and 39 are connected together so that both coils 29 and 35 will always be tuned to the same frequency.

To use the apparatus for receiving signals sent out over the wires Ii! and H, the parts may be connected as shown in Figure 1. In this condition the wire It] is connected through a switch 4| to the condenser 28, and the plate 55 of the tube is connected through a switch 42 to the condenser 21 and resistor 23. At this time the apparatus is substantially identical to that described in my Patent No. 2,389,949 and operates in the same manner.

To use the apparatus for transmitting signals back over the wires Iii and H, the line It may be connected through the switch to the lower end of coil 29 through an inductance 43 and a condenser 44, the inductance 43 being provided to match the impedance of the line during transmission. The plate I5 of the tube may be connected through the switch 42 to a wire 45 connected through a condenser 46 to the upper end of coil 29. The wire 45 may also be connected through a switch 41 and an R. F. choke 48 to the line Hi. There is also provided for transmittin a signal translating device shown as a microphone 49 which is connected through a switch 5I across the grid bias resistor 36. The several switches 4!, 42, t! and BI may be interconnected for simultaneous operation.

In transmitting the switches are all moved to their positions as shown in dotted lines. At this time the heating current and direct current to supply plate voltage are supplied by the wires Ill and I I, but no signal currents are supplied. The filament I2 will be heated in the same manner as that described above, the choke 48 serving to keep the high frequency signal current out of the remainder of the circuit. The plate current of the tube flows through the wire 45 and condenser 46 to the coil 29 which may be tuned by one of the condensers 32 to any desired frequency. This arrangement causes the tube to oscillate at the selected frequency, the oscillations being fed back to the grid through the coil 35. The grid supply voltage may be modulated by impressin an audible or other desired signal on the translating device 49 to modulate the oscillations. The modulated oscillations will be fed back to the circuit I UI I through the condenser 44 and inductance 43 and may be picked up for reproduction at the remote point or at any other point supplied by the circuit I l.il I. It will be understood that this circuit may be either a wired or a wireless circuit, as desired.

Figure 2 illustrates an alternative arrangement which diiiers from Figure 1 principally in that it provides more power for both reproduction and transmission of signals. As shown in this figure,

supersonic heating current and direct current may be supplied over a circuit including a pair of wires 52 and 53. The wire 52 is connected through a tuned circuit including coils 5 and 55 and a condenser 56 in parallel with the coil 55 to the wire 53 through a resistor 57 and a bypass condenser 58 to ground at 59, the wire 53 being grounded at 5|. The winding 55 serves as the primary of a transformer whose secondary winding 62 is connected to the filaments 63 and B4 of a pair of electron discharge tubes 65 and 66. The wire 52 is also connected through a load resistor 61 to the plate 68 of the tube 65.

The tube 65, as shown, is a double tube including a diode section and a tetrode section such, for example, as a 185. The diode section coroprises a plate 69, and the tot-rode section includes in addition to the plate 58 a control grid '4! and a screen grid The tube is illustrated as a p-entode s 11-935 and includes a plate 13, a control grid 34, a screen grid and a suppresser grid 35.

To utilize the circuit for transmitting, which is the condition shown in full lines in Figure 2, the tube 68 serves as an oscillator whose oscillations may be modulated through the tube 55. As shown, the plate is of the tube 35 is connected through a winding Tc having variable condenser 18 in parallel therewith to the line 52. The winding i? may serve as the primary of a transformer whose secondary I9 is connected through a condenser BI across the lines 5253 to transmit 0scillations thereto. The condenser it may be a single variable condenser, as shown, or may comprise a bank of condensers such as those shown at 32 or 38 in Figure 1 to vary the tunin of the circuit. The screen grid 75 is connected through an R. F. coil 82 to the lower ends of the coil I? and condenser I8 and may be connected through a switch 83 and a condenser 84 to the upper end of a coil 85 which is loosely coupled to a coil 86. The coils 85 and 36 may be tuned by a variable condenser 81 connected in parallel therewith by a switch 88, as shown. For transmitting the lower end of the coil 85 is connected through a switch 89 to the cathode 5%, and the upper end is connected through a condenser and a switch 92 to the control grid 4, a "bypass resistor 93 preferably being provided. With the circuit arranged and the switches in the position shown, the tube 66 will oscillate at a frequency determined by adjustment of the condensers it and 8?, and the oscillations will be transmitted to the line through the transformer I9.

To modulate the oscillations a signal translating device such as a microphone 94 is provided connected through a condenser 95 and a switch 96 to the grid H of the tube 65. Preferably a bypass resistor 97 is provided across the grid circuit. The plate 68 of the tube 55 is connected through a condenser 98 and a switch 99 to the suppresser grid 15 of the tube 66 to modulate the oscillations. Preferably, a bypass resistor I0! is connected across the suppresser grid circuit, as shown. With this construction when a signal is impressed on the microphone 94 the signal will be amplified in the tube 65 and impressed on the suppresser grid 16 of the tube 63 to modulate the oscillations produced by the tube 56. The modulated oscillations are impressed on the line 5253 and may be reproduced at any desired remote point.

To use the apparatus for receiving signals the several switches are thrown to the positions op- 75 posite to those shown. An additional switch I02 is-moved simultaneously to connect a condenser I03'across the. coil 86. The switch 99 connects ar-signal reproducing. device such. as a headset I04 to the :plate 68 of the tube 65.. The switch 96 connects the control. grid II of the tube 65 to a wiper on a. potentiometer I05 which is bypassed by-a condenser I66 and the upper end of which is connected to the plate 69 for the diode section of the tube 65. The plate 69 is also connected through a wire I01 and the switch 92 to the upper end of the coil 86.

At this time the tube 66 is inactive and the double tube 65 serves both to detect and to amplify the signal supplied over the wires 52 and 53. For this purpose the wire 52 is connected througha wire I68 and the switch 83 to the tuned circuit provided by the condenser 81, the coils 85 and 86 and the condenser I03. The signal. current passed. by the tuned circuit is connected through the wire I61 to the plate 69 of the tube 65. The current flowing in. the diode section of the tube 65 may be conducted through the variable resistor I65 which serves as a volume control to the control grid II of the tetrode section of this tube. The signal detected is amplified in the tetrode section of the tube and is reproduced. by the headset I04.

In the receiving position, the particular type of tuned circuit formed by the coils 85 and 86 and the condensers 8'! and. I03 enables substantially any desired voltage to be provided at the plate 69 and further enables this voltage to be maintained substantially constant throughout the full range. The incoming signal finds one path to ground through condenser 81 and a second through. coils 85 and 85 and condenser I93 in series. If coil 86 and condenser I93 are tuned exactly to resonance with the signal they appear as a series resonant circuit offering zero impedance between coil 85 and ground. The voltage applied to plate 69 is equal to the drop across the condenser I03 which is equal to and out of. phase with the drop across the coil 86.

If more voltage is desired at the plate 69 the condensers 81 and I03 may be adjusted to increase the capacity of 81 and reduce the capacity of I03. This makes the combination 8I--85 capacitative and the combination 86I63' inducti've to maintain the overall tuning the same. However, the voltage drop across I93 is increased. By proper design of the elements the voltage may be made to increase or decrease at selected frequencies to compensate for varying line attenuation or the like andmaintain the voltage constant at the plate 69 at all frequencies. It will be seen that a circuit of this type would be highly advantageous in the apparatus illustrated as well as in many other types of apparatus.

Figure 3 illustrates still another construction in which the necessity for switching between receiving and transmitting operations is eliminated. The circuit elements as shown in Figure 3 are substantially similar to those of Figure 2 and function in general in the same manner. The leads which connect to terminals on the apparatus are shown at III) and III and supply heating current at supersonic frequency, at least one signal carrier current modulated at an audible frequency and a direct current whose polarity is as indicated. The receiving part of the apparatus includes a tube H2 similar to the tube 65 of Figure 2 having a filament H3, a plate II4, grids H5 and IIS and a plate 1. The filament H3 is connected to a transformer secondary winding I18 which is magnetically coupled to a winding; I I9 having a condenser I 2|; in parallel therewith and connected through a. coil I22 to the wire II I. The coils and; condenser form a circuit tuned to: the heating current frequency and substantially block the signal frequency so that the filament will be heated by the supersonic frequency only. The wire III also connects througha. blocking condenser I23 to a tuned cir cuit including condensers I24 and coils I25 to the plate H4. The. plate is connected through a resistance I26 to the filament and a wiper I21 engages the resistance -I26 to supply a signal voltage through acondenser I28 to the grid II5.

In this way the signal voltage is impressed on the:

tube II 2 which serves to amplify the. signal. The plate II-"I is connected as shown to a signal reproducing device such. as earphones I29 to reproduce the. signal, the other parts of the circuit being substantially identical with the circuit elements at the right of Figure 2 This portion of the circuit serves to receive and re.- produce the transmitting signals without requiring a local power supply.

The transmitting portion of the circuit includes a tube Ir3 I similar to the tube 66 of Figure 2 and having a. filament I32, a control grid I33, a screen grid I34, a suppressor grid. I and a plate I36. The filament I32 is heated by the supersonic heating current through a. transformer secondary Winding I31 connected to the wire III through tuning elements including coils I38 and I39 and condenser MI. The control grid I33 is connected through a tuned circuit shown as including a crystal I42 to the screen grid I34. With this. connection the filament control grid and screen grid act as a triode and the crystal I42 causes the tube to oscillate. Preferably the crystal is tuned to a frequency difiering from both the heating current frequency and the signal frequency. A signal translating device such as a microphone I43 is connected to the suppressor grid I35 to modulate the oscillations. The plate is connected through a circuit including a coil I44 and a condenser I45 tuned to the oscillating frequency to the wire III as shown. A secondary winding I46 coupled to the winding I44 connects through condensers M1 to the wires Ill] and I. II to impress the modulated oscillations thereon.

With this construction when a signal current is applied to the wires II 6 and III at the frequency to which the tuned circuit I24I2-5 is resonant, the signals will be reproduced through the tube H2 at the earphones I29. The signal current will not 'afiect the transmitting parts of the circuit since it is blocked by the tuned circuit. I'M-I45. When it is desired to transmit a signal such as an audiblesignal it may be impressed on the microphone I43 to modulate the oscillations produced by the tube I3I. The modulated oscillations can be transmitted by the wires III) and III to a desired point of reception.

While several embodiments of the invention have been shown and described in detail, it is to be understood that they are illustrative only and are not to be taken as a definition of the scope of the invention, reference being had for this purpose to the appended claims.

What is claimed is:

1. A. signal receiving and transmitting apparatus comprising an electron discharge tube having a cathode, a grid and a plate, terminals connected to the cathode to supply alternating heating current of supersonic frequency thereto, the terminals also being adapted to supply a signal voltage of a'different frequency than the heating current, a microphone, means including a switch selectively to connect the grid of the tube to the terminals or to the microphone, a signal reproducing device, and means including a switch solectively to connect the plate of the tube to the reproducing device to reproduce a signal supplied at the terminals or to the terminals to supply a signal thereto.

2. A signal receiving and transmitting apparatus comprising an electron discharge tube having a cathode, a grid and a plate, terminals connected to the cathode to supply alternating heating current of supersonic frequency thereto, the terminals also being adapted to supply a signal voltage of a different frequency than the heating current, a tuned circuit, a microphone, means including a switch selectively to connect the grid of the tube through the tuned circuit to the terminal to receive the signal or to the microphone for transmitting, a signal reproducing device, and means including a switch selectively to connect the plate of the tube to the signal reproducing device or through the tuned circuit to the grid of the tube to cause the tube to oscillate.

3. A signal receiving and transmitting apparatus comprising an electron discharge tube having a cathode, a grid and a plate, terminals connected to the cathode to supply alternating heating current of supersonic frequency thereto, the terminals also being adapted to supply a signal voltage of a different frequency than the heating current, a tuned circuit resonant to the signal frequenc and anti-resonant to the heating current frequency, means including a switch to connect the terminals through the tuned circuit to the grid of the tube to cause it to respond to the signal voltage, means including a switch to connect the plate of the tube through the tuned circuit to the grid of the tube to cause the tube to oscillate, a signal reproducing device, means includin a switch to connect said device to the plate of the tube to reproduce the signals, a microphone, and means including a switch to connect the microphone to the tube to modulate the oscillations thereof.

4. A signal receiving and transmitting apparatus comprising an electron discharge tube having a control circuit and an output circuit, a filament in the tube to supply power thereto, terminals adapted to be connected to a source of alternating heating current, means connecting the filament to the terminals to be heated by the heating current, a tuned circuit, a signal translating device, a signal reproducing device, and switch means to connect the terminals through the tuned circuit to the control circuit and the signal reproducin device in the output circuit in one position and in another position to'connect the output circuit through the tuned circuit to the control circuit to cause the tube to oscillate, to connect the translating device to the control circuit to modulate the oscillations, and to connect the output circuit to the terminals to impress the modulated oscillations thereon.

5. A signal receiving and transmitting apparatus comprising an electron discharge tube having a control circuit and an output circuit, a filament in the tube to supply power thereto, terminals adapted to be connected to a source of alternating heating current, the terminals being adapted to supply signal current at a frequency different than that of the heating current, means including a circuit resonant at the heating current frequency and anti-resonant at the signal means to connect the terminals through the tuned circuit to the control circuit and the signal reproducing device in the output circuit in one position and in another position to connect the output circuit through the tuned circuit to the control circuit to cause the tube to oscillate, to connect the translating device to the control circuit to modulate the oscillations, and to connect the output circuit to the terminals to impress the modulated oscillations thereon.

6. A signal transmitting apparatus comprising an electron discharge tube having an input circuit and an output circuit, a filament in the tube, terminals adapted to be connected to a source of alternating heating current, means connecting the terminals to the filament to supply heating current thereto, resonant means connecting the input and output circuits of the tube to cause the tube to oscillate at a frequency different than that of the heating current, a signal translating device connected to the tube to modulate the oscillations, and means connecting the output circuit of the tube to the terminals to impress the modulated oscillations thereon.

7. A signal transmitting apparatus comprising an electron discharge tube having an input circuit and an output circuit, a filament in the tube, terminals adapted to be connected to a source of alternating heating current, resonant means connecting the input and output circuits of the tube to cause the tube to oscillate at a frequency different than that of the heating current, means resonant at the heating current frequency and anti-resonant at the oscillating frequency connecting the terminals to the filament to supply heating current thereto, a signal translating device connected to the tube to modulate the oscillations, and means resonant at the oscillating frequency and anti-resonant at the heating current frequency connecting the output circuit of the tube to the terminals to impress the oscillations thereon.

8. A signal transmitting apparatus comprising an electron discharge tube having a filament, a plate and a plurality of grids, terminals adapted to be connected to a source of alternating heating current, means connecting the terminals to the filament to supply heating current thereto, resonant means interconnecting two of the grids to cause the tube to oscillate at a frequency different than that of the heating frequency, a signal translating device connected to a third grid to modulate the oscillations, and means connecting the plate to the terminals to impress the oscillations thereon.

9. A signal receiving and transmitting apparatus comprising an electron discharge tube having a filament, a plate and a grid, terminals adapted to be connected to a source of alternating heating current, means connecting the terminals to the filament to supply heating current thereto, the terminals also being adapted to supply a signal current at a frequency different than that of the heating current, a tuned circuit resonant at the signal current frequency, a signal reproducing device, a signal translating device, and switches having one position in which they connect the terminals through the tuned circuit to the grid of the tube and the signal reproducing device to the plate of the tube and another position in which they connect the plate and grid through the tuned circuit to cause the tube to oscillate, the plate to the terminals to impress the oscillations thereon and the signal translating device to the grid to modulate the oscillations.

10. A signal receiving and transmitting apparatus comprising a first electron discharge tube having a filament, a plate and a grid, a second electron discharge tube having a filament, a plate and a plurality of grids, terminals adapted to be connected to a source of alternating heating current, means connecting the terminals to the filaments of the tubes to supply heating current thereto, the terminals also being adapted to supply a current at a frequency different than that of the heating current, a tuned circuit resonant at the signal current frequency, a signal reproducing device, a signal translating device, and means including switches having one position in which they connect the terminals to the grid of the first tube and the signal reproducing device to the plate of the first tube and a second position in which they connect two grids of the second tube through the tuned circuit, the plate of the second tube to the terminals, the grid of the first tube to the signal translating device, and the plate of the first tube to a grid of the second tube.

11. A signal receivin and transmitting apparatus comprising a pair of terminals adapted to be supplied with alternating heating current at one frequency and with signal currents at difierent frequencies, electron discharge means including filament, grid and plate elements, means offering a low impedance to the heating current and a high impedance to the signal currents connecting the terminals to the filament elements, circuit means tunable to signal current frequency to connect the terminals to a grid element, a signal reproducin device to be connected to a plate element to reproduce the signals, circuit means to connect to elements including at least one grid element to cause oscillations at a frequency different that the heating current frequency, a signal translating device to be connected to a grid element to modulate the oscillations, and circuit means to connect the plate element to the terminals to impress the modulated oscillations thereon.

12. A signal recieving and transmitting apparatus comprising a pair of terminals adapted to be supplied with alternating heating current at one frequency and with alternating signal current at a diiierent frequency, a pair of electron discharge tubes each including a filament, a grid and a plate, means offering a low impedance to the heating current and a high impedance to the signal current connecting the terminals to the filaments to heat them, circuit means tunable to the signal current frequency to connect the terminals to a grid of one of the tubes, a si al reproducing device to be connected to the plate of said one of the tubes, circuit means tunable to a frequency to be connected to the other tube to cause it to oscillate, a signal translating device, means to connect the translating device to a grid of the other tube to modulate the oscillations, and means to connect the plate of the other tube to the terminals.

13. The construction, defined in claim 12 in which the last named means comprises a tuned circuit tuned to the oscillating frequency.

14. A signal receiving and transmitting apparatus comprising a pair of terminals adapted to be supplied with alternating heating current at one frequency and with alternating signal current at a different frequency, a pair of electron discharge tubes each including a filament, a grid and a plate, means offering a low impedance to the heating current and a high impedance to the signal current connecting the terminals to the filaments to heat them, a circuit tuned to the signal frequency connecting the terminals to a grid of one of the tubes, a signal reproducin device connected to the plate of said one of the tubes, a circuit tuned to a frequency different than the heating and signal frequencies connected to the other tube to cause it to oscillate, a signal translating device connected to a grid of the other tube to modulate the oscillations, and means connecting the plate of the other tube to the terminals to impress the modulated oscillations thereon.

15. The construction defined in claim 14 in which the last named means is a tuned circuit tuned to the oscillating frequency.

16. In an electric signal handling apparatus, a tuned circuit across which a signal is impressed comprising two parallel branches, a reactance 4 element in one of the branches, three reactance elements in series in the other branch, two of which are tunable to provide a series resonant circuit, and an output connection between said two reactance elements.

17. In an electric signal handling apparatus, a tuned circuit across which a signal is impressed comprising two parallel branches, a condenser in one of the branches, an inductor and a condenser in series in the other branch, and an output connection between the inductor and the condenser.

18. In an electric signal handling apparatus, a tuned circuit across which a signal is impressed comprising two parallel branches, a reactance element in one of the branches, a pair of reactance elements in the other branch tunable with each other and with the first named reactance element to resonance with the signal, and an output connection between the pair of reactance elements.

HARRY W. BECKER.

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

UNITED STATES PATENTS Number Name Date 2,020,297 Buckley Nov. 12, 1935 2,176,868 Boswau Oct. 24, 1939 2,190,546 Loube Feb. 13, 1940 2,288,487 Rosen June 30, 1942 2,346,504 Place Apr. 11, 1944 2,389,949 Becker Nov. 27, 1945

Patent Citations
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US2176868 *15 Mar 193724 Oct 1939Lorain Telephone CompanyRadio communication system
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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2756330 *7 Oct 195024 Jul 1956Conn Ltd C GElectrical tone source for musical instruments
US2766381 *29 Oct 19549 Oct 1956Weston Electric Ind CorpMarker signal generator
US2837636 *8 Mar 19543 Jun 1958Jr Joseph D RichardRadio test signal generation
US2866162 *25 Jul 195523 Dec 1958Tele Dynamics IncOscillator-modulator circuit
US2873312 *18 Oct 195110 Feb 1959Time IncModulator with photoelectric signal source and compressor for facsimile
US2943188 *27 May 195328 Jun 1960Ultra Electric IncTransmitter-receiver for radio location
US3167711 *3 Jun 196426 Jan 1965Wright Paul NTransceiver having means for neutralizing inherent distributed capacity
Classifications
U.S. Classification455/87, 455/84, 455/92, 331/179, 331/73, 455/352, 332/182, 331/167
International ClassificationH04B1/40
Cooperative ClassificationH04B1/40
European ClassificationH04B1/40