US1739340A - Signaling system - Google Patents

Description

G. P. ADAIR Dec. 1O, 1929.

SIGNALING SYSTEM Filed Feb. 18 1928 AMPL/F/ER Invent-or: George F1 Adam Hus Attorney.

Patented Dec. 10, 1929 UNITED ST ES PATENT OFFICE I GEORGE I. ADAIB, OF BGHENECTADY, NEW YORK, 'ASSIGNOR '10 GENERAL ELECTBIC COMPANY, A CORPORATION 01' NEW YORK SIGNALIN G SYSTEI Application filed February 18, 1928. Serial No. 255,484.

My invention relates to signaling systems and more particularlyto high frequency communication systems of the duplex type in which automatic means are provided for controlling the volume of the signal which is received from remote points and for protecting the receiving equipment against energy which reaches it from the associated transmitter.

Still more particularly my invention relates to systems of the type disclosed in application Serial N 0. 161,191 of Lester F. Bird, filed J anuary'li, 1927 and which is assigned to the same assignee as the present application. In thatapplication a device is disclosed comprising a three element electron discharge device, the anode-cathode circuit of which comprises a shunt to the receiving channel. The potential of the grid of this device is controlled by a resistance whichis connected in series with the discharge path of both the detector of the receiving circuit and the oscillation generator of the associated transmitter. In this way the impedance of the three element device may be controlled both in response to the signal intensity as indicated by the magnitude of the detector anode current and totthe functioning of the oscillation generator. Thus this shunt connected control device in the receiving circuit serves both to protect the receiver against energy which reaches it from the associated transmitter and also to control the volume of the received signal.

While the device disclosed by Mr. Bird in the above application has proved to be a very satisfactory onein commercial practiceIhave found that certain simplifications in the circuit may be made which result in improved operation of the system as a whole and at the same time in reduced cost of construction and maintenance.

The novel features which I believe to be characteristic of m invention will be set forth with particufarity in the appended claims. My invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawmg, in WhlCll the single figure represents an embodiment of my invention.

Referring to the drawing 1" represents a portion of the transmitter circuit and 2 the essential elements of the associated receiving c rcuit to which I have applied my invention. In the receiving circuit I have shown an electron discharge device 3, which is employed as a detector. The input circuit to this detector is supplied with received signal currents through a channel which includes the conductors 4, which lead to any suitable .antenna or wire line circuit, such as a power distribution system from which the signals are received, 6. The secon ary winding of this transformer is connected through condensers 7 and 8 the latter of whichis connected in parallel with resistance 17 to the grid and cathode respectively of the electron discharge devlce 3. The output currents from this discharge device are supplied from the anode c1rcuit,thereof through the transformer 9,

hybrid coil 10 and output circuit 11 to anythereof through the choke coil 15, source of potential 16, resistance 17, conductor 18, spacebetween the cathode and anode of control electron discharge device 19, conductor 20 and the space between the cathode and anode of discharge device 12. Signal currents from any suitable signaling device or telephone instrument may be impressed upon the grid of the control device 19 through the circuit 11, hybrid coil 10 and amplifying means 21. These currents will also be caused laybrid coil 5 and transformer to modulate the currents which are produced b153 1 the oscillation generator 12 by any suite means, not shown. One means whereby this modulation may be eflected is illustrated in Patent No. 1,696,590, L. F. Bird, issued December 25, 1928. Condenser 28 is connected between the anode and cathode of device 19 to prevent modulation of the transmitter output currents by this device. Energy is supplied for heating the cathodes of the discharge devices .12 and 19 through suitable cathode transformers 22 and 23.

In the receiving circuit an electron discharge device 24 of the two element type, or of the three element type, in which the grid and anode are connected together to constitute a single electrode is connected in shunt with the receiving circuit and hence in shunt with the tuned circuit 25, which comprises the input circuit of the detector 3. The anode circuit of the device 24 is suitably biased with respect to the cathode thereof by means of a source of potential 26, such that the device has no substantial effect upon signals which are received having substantially normal intensity. This bias, however, is such that it is overcome by signals of greater than normal intensity, which thereby cause the impedance between the anode and cathode of this device to be diminished. This diminution of the impedance causes the device 24 to become an effective bypassfor a portion 0 the signal currents'and a shunt upon the tuned circuit 25. The sharpness of the tuning of circuit 25 is then lessened and this eflect together with that of bypassing a portion of P the signal currents serves to diminish the intensity of the signals whichreach the grid of detector 3. The impedance of this shunt path will of course be dependent upon the intensity of the received signal and will vary therewith. .Thus to signals which are received having normal intensity, the device 24 is ineffective to produce any substantial diminution thereof, but as soon as signals of greater than normal intensity are'received the impedance of the device 24 becomes diminished, thereby causing a portion of these signals to .be short circuited through the device 24, and

the tuned circuit to be affected. In this way a very effective volume control of the received signals may be had. 7

This device is also caused to respond to operation of the transmitting circuit. It will be noticed that the resistance 17 is connected between the cathode and anode of the device 24 and is also connected in series with the discharge path of the oscillation generator 12.

' Thus whenever current flows in the discharge path of the oscillation generator a potential will appear across the resistance 17 having the olarity indicated on the drawing and tending to drivethe anode thereof strongly positive with respect to the cathode. In t is way the impedance of device 24 is greatly shunt circuit of low impedance to currents which reach the receiver and also causes the tuned circuit to be affected in the manner described. '].lhus the receiving circuit is rendered insensitive to excessive and disturbing potentials which may rea ch it from the transmitting circuit during operative periods thereof.

Current is caused to flow in the discharge path of the oscillation generator by means of the control device 19 upon which the voice currents are impressed. This device normally has sufiicient impedance between its cathode and anode to preclude the flow of anode current through the oscillation generator and hence to preclude the operation of the device 12. When the operator speaks into the microphone voice currents will be supplied through the audio amplifier 21 to the grid of device 19. The impedance between the anode andcathode thereof will then be reduced and current will becausedto flow in the circuit previously traced including'the anode, cathode circuit of the device 12 and the resistance 17 thereby causing the initiation of high fref ceiving circuit and the tuning of the circuit to be affected.

Thus the device24 serves in a dual capac- 'ity, acting as a volume control means during eriods of reception of signals from a remote statiofi'and as a means for rotecting the re ceiver against excessive an disturbing v'oltages which reach it from the transmitter during periods of transmission. The circuits of device 24 may be separately adjusted in a "manner which permits most efficient operation of the device in both of its dual functions. Thus the source of potential 26 may be varied in a manner to permit best operation of the tube as a volume control device and the value of resistance 17 may be adjusted to permit best operation as a protective device.

I The operation of the device is entirely independent of that of the detector and hence. it is not subjected to any irregularities in the functioning of that device. A normal detector circuit may be employed. It will be noticed that the cathodes of the control device and detector are always at the same potential. Hence a common cathode source of potential may be employed and the expense of providing and maintaining a separate battery for each device is eliminated.

While I have shown and described a single embodiment of my invention it will, of course, be understood that I do not wish to be limited thereto since many modifications, both in the circuit arrangements and in the instrumentalities employed maybe made without departing from the spirit and scope of my in vention as set forth in the ap ended claims.

What Iclaim as new and esire to secure by Letters Patent of the United States, is:

1. In a signaling system, a receiving circ'uit, a transmitting circuit, an electron discharge device having an anode and a cathode, the space between said anode and cathode being connected in shunt with said receiving circuit and the impedance thereof being variable in response to the intensity of the received signals, and means responsive to oper ation of said transmitting circuit for impressing a potential upon said anode with respect to said cathode thereby to diminish the impedance'of said discharge device.

2. In a signaling system, a receiving circuit, a transmitting circuit, an electron, discharge device having an anode and a cathode, the space between said anode and cathode being connected in shunt with said receiving circuit, means for biasing said anode with respectto said cathode such that said device has substantially no effect upon received signals of normal intensity but has diminishing impedance to signals of greater than normal intensity, aresistance connected between said anode and cathode and means responsive to operation of said transmitting circuit for causing a current to flow through said resistance to diminish the impedance of said discharge device thereby to effect the intensity of currents flowing through said receiving circpit.

3. In a signalingsystem, a receiving circuit and a transmitting circuit, said transmitting circuit including a normally inoperative electron discharge oscillation generator,

an electron discharge device connected in shunt with said receiving circuit having an anode and cathode, means for blasm sald anode with respect to said cathode suc that said device has substantially no eflect upon .received signals of normal intensity-but has diminishing impedance to currents. of intensitygreater than normal, and a resistance connected between said anode and cathode, said resistance beingalso connected in series with the discharge path of said oscillation generator' whereby said receiving circuit is rendered insensitive dur ng operatlve-perlods of said osclllatlon generator.

4. In a signaling system, a transmitter and a receiver, a tuned input circuit to said receiver, a two electrode electron discharge device having an anode and cathode connected in shunt with said tuned circuit, said device havin impedance such that it has no substantial 'eEect upon received signals of normal intensity but which diminishes in response to signals of intensity greater than normal, and means for producing. a positive. potential upon said anode with respect to said cathode responsively to operation of said transmitter to diminish the impedance of said device,

thereby to cause said device to constitute a low impedance shunt across said rec'eiving circuit and to affect the tuning of said input circuit.

Images