US2282404A - Transmission system - Google Patents

Transmission system Download PDF

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Publication number
US2282404A
US2282404A US290088A US29008839A US2282404A US 2282404 A US2282404 A US 2282404A US 290088 A US290088 A US 290088A US 29008839 A US29008839 A US 29008839A US 2282404 A US2282404 A US 2282404A
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United States
Prior art keywords
channel
tube
signal
transmission
circuit
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Expired - Lifetime
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US290088A
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English (en)
Inventor
Roswell H Herrick
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Associated Electric Laboratories Inc
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Associated Electric Laboratories Inc
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Filing date
Publication date
Priority to BE464852D priority Critical patent/BE464852A/xx
Application filed by Associated Electric Laboratories Inc filed Critical Associated Electric Laboratories Inc
Priority to US290088A priority patent/US2282404A/en
Priority to GB12372/40A priority patent/GB541981A/en
Application granted granted Critical
Publication of US2282404A publication Critical patent/US2282404A/en
Priority to FR930807D priority patent/FR930807A/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/20—Reducing echo effects or singing; Opening or closing transmitting path; Conditioning for transmission in one direction or the other

Definitions

  • the present invention relates generally to improvements in signal current transmission systems of the type in which signal controlled switching circuits are provided for partially or completely blocking, under certain conditions, certain of the'signal current channels included therein and, more particularly, to improvements in telephone substation circuits having incorporated therein coupled signal current channels for the transmission of incoming and outgoing signal currents.
  • a hybrid system or antiside tone impedance network is provided for preventing signal currents developed during operation of the transmitter from being transmitted to the receiver and for preventing signal currentslincoming over the line extending to the substation from being transmitted to the transmitter.
  • one of the factors which determines the efficiency of the side tone suppression is the impedance of the talking circuit established by way of nal currents transmitted in the opposite direction. In other words, conversation break-ins are positively prevented.
  • This impedance is not the same for any two different connections and, accordingly, the hybrid system of each substation is usually balanced to provide maximum side tone suppression eciency for average line conditions.
  • theconditions of unbalance introduced into the substation circuit by the impedances of the lines over which an established connection extends may become intolerable. This is particularly true in substation installations provided in an exchange area where the subscribers lines are of widely diierent lengths.
  • signal controlled switching means may be provided in the substation circuit for selectively blocking the signal transmission channels when not in use.
  • the transmission channels are completely blocked when not in use. More particularly, during intervals when the transmitting means of the substation is being used to trans- 'mit outgoing signal currents, the incoming signal current channel is rendered completely inactive. Conversely, during those periods when signal currents are incoming to the substation, the transmitting channel is rendered completely inactive.
  • An arrangement of this character prevents any interruption of a speech train being transmitted in one direction in response to sigrent channels are normally active and the transmission efliciencies of the two channels are varied in' opposite senses by varying the plate or anode impedances of electron discharge control tubes respectively coupled thereto in response to signal currents traversing either of the two channels.
  • a telephone substation circuit which is adapted to be connected to an associated line and comprises the usual transmitting and receiving means.
  • circuit also includes a transmission system which channel and a second leg shunting a portion of the channel.
  • One leg of each of the two voltage ⁇ dividers is bridged by an adjustable impedance in the form of the space current path of an associated electron discharge tube, whereby the signal current transmission eiciencies of the two channels are variable with variations in the output electrode impedances of the respective associated tubes.
  • the control electrodes of the two tubes are normally biased to potentials such that i the associated channels are both active, a control circuit being provided for varying the control electrode potentials in response to signal currents traversing one of the channels so that the gain or signal current transmission efficiency of the one channel is substantially increased and the signal current transmission eiiiciency of the other channel is substantially decreased.
  • control circuit further includes apparatus comprising one of the two control tubes for varying the transmission efficiency of the channel in use inversely in accordance with the amplitude of the signal input thereto, thus providing automatic gain control action. More-particularly, automatic gain control is achieved by varying .the bias on the control tube associated with the channel in use to vary the output electrode impedance thereof so that the transmission efliciency of the channel is changed inversely in accordance with the signal input thereto.
  • FIG. 1 illustrates a substation circuit having incorporated therein certain of the features of the invention as briefly outlined above;
  • Fig. 2 illustrates a modified form of the improved substation circuit;
  • Fig. 3 illustrates a modication of the circuit arrangement shown in Fig. 2.
  • the substation circuit there illustrated is adapted to be connected to a telephone line terminating at the terminals
  • the substation circuit comprises a transmitter or microphone and receiving means in the form of a loud speaker
  • 02 is of the well-known moving coil type having embodied therein a voice or signal current coil
  • 05 comprises a vacuum tube amplifier
  • This channel further comprises a voltage divider in the form of a potentiometer resistor
  • 09 comprises an electron discharge tube
  • 0 similarly comprises an electron, discharge tube
  • 9 are coupled to the outgoing signal current terminals of the hybrid system
  • a cathode biasing circuit comprising a resistor
  • Operating voltages are impressed upon the anode and screen electrodes of the two tubes
  • This source is by-passed for signal currents in the amplier stages
  • 06 is coupled to the incoming signal current terminals of the vider in the form of a potentiometer resistor
  • 29 comprises an electron disc harge tube
  • the positive terminal of the anode currentv supply source is connected to the anode
  • 40 which is shunted by a by-pass condenser
  • 43 are provided.
  • this circuit comprises an amplifier
  • 50 is impressed upon the control electrode of the tube
  • the indicated control electrodes are normally biased to the desired negative potentials through the provision of small C batteries
  • 52 are connected to control the gains or signal current transmission efficiencies of the two channels
  • 52 are bridged across the series leg H23 of the voltage divider
  • anode current is delivered to these two tubes through high impedance iron core inductors
  • 52 is further isolated through the provisionA of a third high impedance iron core inductor
  • the last-.mentioned impedance element is chosen to present an extremely high impedance to signal currents, whereby the condenser
  • This element is also constructed to have a very low direct current resistance whereby no substantial bias is impressed upon the cathode of the tube
  • 52 are arranged to control the transmission eiliciencies of the signal current channels
  • the output electrode impedance that is, the impedance between the anode and cathode of the tube
  • this potential is adjusted or changed to lower the output electrode impedance of the tube
  • 0I from the sound waves impinging upon the diaequivalent impedance formed by the combination of this impedance andthe resistance of the shunt leg
  • a lesser percentage of the available signal voltage is im ⁇ pressed upon the input electrodes of the power amplier
  • 05 is reduced when the output electrode impedance of the tube
  • 06 is variable directly in accordance with variations in the output electrode impedance of the tubeA
  • 52 isv increased from a normal value to a higher value the equivalent impedance of this output electrode impedance as combined with the resistance of the leg H2B is increased, whereby the signal current flow. through the shunt leg H2 of the voltage divider llll is decreased to produce a corresponding decrease in the signal voltage impressed across .the input electrodes of the amplier tube H9.
  • v if the output electrode
  • 05 is variable inversely in accordance with variations in the output electrode impedance of the tube
  • 52 are biased to a point slightly above anode current cut-ofi so that the output electrode impedances thereof are relatively high. With the two tubes biased in this manner the transmission eiciencies yol the two channels
  • both channels are normally capable of transmitting signal currents with reasonably good eillciency b'ut are insufficient to permit local oscillation of the circuit even when the hybrid system is greatly unbalanced.
  • 09 and l0 are amplified by the tandem connected amplifier units
  • the line conditions of the lines interconnecting the illustrated substation circuit with another distant .substation are such that the hybrid system is substantially unbalanced the mag output electrode impedance l network comprising a resistor
  • This circuit is provided with two this diiliculty. More particularly, the signal voltage impressed across the input electrodes of the amplifier tube 4 is also impressed across the input terminals ofthe amplier
  • control tubes corresponding to the tubes
  • the output electrodes of one of the two tubes are bridged across the series leg
  • 42 are bridged across the shunt leg
  • 06 may be decreased during use of the channel
  • 42 causes the transmission eniciency of the channel
  • 42 is identical in arrangement to the control circuit
  • the magnitude .of the incoming signal currents when amplified by the amplifier unit
  • 05 is decreased and the transmission efficiency of the channel
  • a substantial portion of the signal currents incoming to the substation circuit are transmitted through the channel
  • the person using the substation circuit illustrated is expected to stop speaking.
  • 43 operates further to decrease the transmission eiciency of the channel and further to increase the transmission efciency of the channel
  • this circuit comprises a transmitter or microphone 20
  • the circuit further comprises two control circuits. 242 and 243 which respectively correspond to the control circuits
  • the transmission channel 205 comprises a, coupling transformer 201, an adjustable signal level controlling voltage divider 2
  • the channel 206 similarly comprises a coupling transformer 228,
  • 4 are connected across the adjustable shunt leg 2
  • 4 are coupled to the outgoing signal current terminals of the hybrid system 203 through the voltage transformlng circuit 2
  • 33 included in the incoming signal current chaniel 206 comprises a pair of input electrodes which ire bridged across the adjustable shunt portion l3
  • the )utput electrodes of the tube 233 are coupled hrough the voltage transforming circuit 235 to .he primary winding of the transformer 236, a xy-pass condenser 222 being provided for byiassing .signal currents around the source of inode and screen potential which is connected to he terminal marked +B.
  • the two control circuits 2412 andl 243 are ofY dentical arrangement and for this reason only he details of the control circuit 243 have been illustrated.
  • this circuit comprises a pair if electron dscharge tubes 25
  • the output electrodes of the tube 252 are bridged across the shunt leg 2
  • Anode potential is impressed upon the anode of the tube 252 over a path including the high im.. pedance iron core choke coil 228 and a resistor 229'.
  • anode potential is impressed upon the anode of the tube 25
  • and 252 are controlled by varying the potentials impressed upon the control electrodes thereof.
  • acircuit which includes a transformer 260 having its primary winding bridged across the channel 205 and its secondary windings in-v cluded in a rectifying circuit which also includes a pair of load resistors 26
  • and 262 are bridged by a smoothing condenser 264 so that pulsating direct current developed causes a resonably smooth direct voltage t be developed across the two load resistors.
  • and 262 during signal current transmission through the channel 205 are utilized to control the potentials impressed upon the conthe other hand, is such that the control tube 25
  • alternating signal currents traverse the rectifying circuit including the rectifier 263 and the resistors 262 and 26
  • This automatic gain control circuit comprises a portion or all of the resistor 26
  • a coupling path including a direct current blocking condenser 210 and a resistor 21
  • and 252 are normally biased to have high and low output electrode impedances respectively. Since the output electrode impedance of the tube 25
  • any desired normal ratio between the transmission eiilciencies'of the two channels 205 and 206 may, within limits, be attained.
  • the apparatus at normal if a user of the substation circuit speaks into the microphone 20
  • the average amplitude of current traversing this rectifying circuit obviously varies directly in accordance with the average magnitude of the amplified signal currents.y
  • the rectifier 269 is so Apoled that the current traversing the auxiliary rectifying circuit is in opposition to the current traversing the primary rectifying circuit which includes the rectifier 263.
  • the indicated control cir- Y cuit responds to the signalv'curr'e'nts traversing the channel 205 by substantially decreasing the transmission efiiciency of the channel 206 'and substantially increasing the trans"- mission efiiciency'of .the channel 205. More parnet voltage across the resistor 26
  • the currents traversing the auxiliary rectifyng circuit tend to increase to produce a corresponding decrease in the bias on the control electrode of the. tube 252 so that the output electrodeimpedance of this tube is decreased to lower the transmission efliciency of the channel 205 and. thus decrease the amplitude of the signal current delivered to the auxiliary rectifying circuit.
  • is accompanied by a decrease in the magnitude of the signal currents impressed upon the auxiliary rectifying circuit so that an increase occurs in the biasing voltage of the tube 252, whereby the output electrode impedance of this tube is increased to produce an increase in the transmission eiiiciency of the 'channel 205.
  • the characteristics of the auxiliar-y rectifier 269 are so chosen that the automaticv gain control action just described is not started until the signal currents traversing 'the channel 205 reach an appreciable magnitude.
  • a rectifier of the copper oxide or dry disk type may be accomplished by varying the ticularly, a portion-of the ampliiied signal curl rents'are delivered through the coupling transformer 260 to the rectifying circuit including the rectifier 263, whereby biasing potentials are developed across the load resistors 26
  • the condenser 26,4 is initially charged at an extremely high rate so that the biasing potentials are available immediately speech transmission through the channel 205 is started.
  • the voltage developed across the resistor 262 is poled so that the normal bias impressed upon the control electrode of the tube 25
  • the transmission efflciency of the channel 206 is decreased.
  • functions to increase the negative bias upon the control electrode of the tube 252 so that the stantially nonlinear and no substantial current number of disks included therein, it being well understood in the art that the voltage-current characteristic ⁇ of a rectifier of this type is subfiow therethrough occurs until-a voltage of predetermined magnitude is impressed thereacross. but when this magnitude of voltage is exceeded the current rises steeply with increasing applied voltage.
  • no current flow through the circuit including output electrode impedance of this tube is inrectifier 269 functions to maintain the signal output level of the channel 205 substantially constant regardless of wide fluctuations in the intensity of the signal input to this channel.
  • a portion of amplified signal voltage is impressed this rectifier will occur to start the automatic gain control action until the signal transmission level reaches a desired value.
  • the level of signal transmissionthrough the channel 205 is lowered somewhat by virtue of the inclusion of the voltagetransforming circuit 2
  • the net signal voltage impressed across the outgoing signal current terminals of the hybrid system 203 is the difference between the signal voltage impressed across the primary winding of the coupling transformer 260 and thesignal voltage drops across the two series resistors 2
  • the purpose of providing this voltage transformingcircuit is that of substantially reducing the magnitude of signal currents transmitted to the rectifying circuit including the rectifier 263 through the coupling afforded by unbalance in the hybrid system 203 when signal currents are transmitted to the substation circuit from a distant substation.
  • the control circuit 242 responds to the signal currents transmitted thereto over the channel 206 by operating to lower the transmission eciency of the channel 205 and to increase the transmission efficiency of the channel 206 in a manner identical with that just described with reference to the circuit 243.
  • the input terminals of the control circuit 242 are coupled directly to the loud speaker 202, which speaker, being of the moving coil type, may function both as a transmitter and a receiver. Accordingly, sound waves impinging upon the diaphragm of this speaker cause signal voltages to be developed which are transmitted through the coupling transformer 236 and the voltage transforming circuit 235 to the input terminals of the control circuit 242. Due to the voltage reducing action of theA circuit 235, however, the magnitude of such currents is so low as to cause no substantial response on the part of the conitrol circuit 242.
  • and 252 causes are transmitted through the hybrid system 203 to the channel 206 and the control circuit 242 responds thereto by operating to decrease the transmission efficiency of the channel 205 and to increase the.transmission efficiency of the channel 206.
  • the rectifying circuit includes a single resistor 36
  • the voltage drop across the rectifier 363 functions as the voltage for controlling the bias potentials of the two control tubes 35
  • 'Ihis particular arrangement of the rectifying circuit is well adapted to the use of a vacuum tube diode as the rectifying element.
  • the circuit is arranged so that the output electrode impedances of the two control tubes 35
  • the increase in the transmission eiciency of the channel 205 is such that the signal currents developed through operation of the microphone 20
  • which funceflciency of the channel 306, are coupled to the series leg 33
  • the transmission eciency of the channel 305 is relatively low.
  • the indicated transmission efciencies of the two channels may. be adjusted to any desired normal ratlo.
  • the resulting signal currents are transmitted through the transformer 381, the voltage divider 3I2 and the tube 3I4 to the coupling transformer 360, thereby to cause rectified signal currents to traverse-the rectifying circuit including the rectifier 363.
  • the voltage developed across the rectier 363 increases thenegative bias upon the control electrodes of each of the two tubes 35
  • the transmission emciency of the channel 305 is increased and the transmission eiiicienc'y oi' the channel 3061s decreased in a.
  • a pair of channels for transmitting signal currents in different directions, an electron discharge tube including a control electrode and a pair of output electrodes coupled to one of said channels, a second velectron discharge device including a control electrode and apair of output electrodes coupled to the other of said channels, the output 4electrode impedances of said tubes-being variable in accordance with changes in the potentials impressed upon the control electrodes thereof to vary the signal currenttransmission eliiciencies of the respective associated channels, means responsive to signal currents traversing said one channel for varying the potentials upon said control electrodes to increase the signal current transmission eihciency of said one channel and to decrease the signal current transmission efficiency of said other channel, and means controlled in accordance with the amplitude of signal currents traversing said one channel for further controlling the output electrode impedance of the tube associated with said one channel to vary the signal current transmission efficiency of said onechannel inversely in accordance with the amplitude of the signal input thereto.
  • a signal current transmission channel an electrondischarge tube including a pair of output electrodes, means for 'coupling said output electrodes to said lchannel so that the signal current transmission eiliciency of said channel is changed in one sense in response to an increase in the output electrode impedance of said tube and is changed in an opposite sense ,in response to a decrease in the output electrode impedance of said tube, means responsive to signal currents traversing said channel for changing the output electrode impedance of signal voltages upon said control electrodes to vary the potentials thereof in opposite senses such that the output electrode impedance of the tube associated with said one channel is increased and the output electrode impedance of the tube associated with said other channel is decreased when signal currents ltraverse said one channel, and means comprising a voltage transforming circuit included in said one channel at a point between said one point and said coupling means for preventing signal currents transmitted through said other channel and fed through said coupling means to said one channel from substantially changing said potentials.
  • a pair of channels for transmitting signal currents in diierent directions, an electron discharge tube including a control electrode and a pair of output electrodes coupled to one of said channels, a second electron discharge device including a control electrode and a pair of output electrodes coupled to the other of said channels,- the output electrode imsaid tube substantially to increase the signal current transmission eiciency of said one channel, and means controlled in accordance with the amplitude of signal currents traversing said channel for further controlling the output electrode impedance of said tube to vary the signal current transmission eiiiciency of said channel inversely in accordance with the amplitude of the signal input thereto.
  • InV a transmission system, a signal current transmission channel, an electron discharge tube including a pair of output electrodes and a control electrode for changing the impedance across said output electrodes, means for coupling said output electrodes to said channel so that the signal current transmission eiciency of said channel is changed' in one sense in response to an increase in the output electrode impedance of said tube and is changed in an opposite sense in response to a decrease in the output electrode impedance of said tube, means for impressing a biasing potential upon said control electrode,
  • an electron discharge tube including a pair oi' output electrodes and a control electrode for changing the impedance across said output electrodes, means for coupling said output electrodes to said channel so that the signal current transmission eiiciency.
  • said chan- Vnel is changed in one sense in response to an increase in the output electrode impedance of said tube and is changed in an opposite sense in response to a decrease in the output electrode impedance of said tube, means for impressing a biasing potential upon said control electrode, a control circuit coupled to said one channel and including signal voltage .rectifying means and a circuit element Afor impressing the rectied signal voltage upon said control electrode to vary the potential of said control electrode in a direction substantially to increase the signal current transmission eiliciency of said channel when signal currents traverse said channel, and a second control circuit including at least a portion of said circuit element and additional rectifying means for further controlling said potential to vary the Signal current transmission eiiiciency of said channel inversely in accordance withtheampli- ⁇ tude of
  • a pair of channels for transmitting signal currents in different directions a voltage divider included in'each of said channels, each of said-dividers including a series leg and a shunt leg, a pair of electron discharge ⁇ cies of said channels are respectively variable directly in accordance with the output electrode impedances of the respective associated tubes, means for impressing biasing potentials upon said control electrodes, means responsive to signal currents traversing one of said channels for varying said potentials in opposite senses such that the output electrode impedance of the tube associated with said one channel is increased and the output electrode impedance of the tube associated with said other channel is decreased, and means controlled in accordance with the amplitude of signal currents traversing said one channel for further controlling the output electrode impedance of the tube associated with said one of said tube and is changed in the opposite sense in response to a decrease in the output electrode limpedance of said tube, means responsive to signal currents traversing said channel for changing said impedance in a direction substantially to increase the signal current transmission ei
  • Telephone substation apparatus comprising transmitting means, receiving means and a hybrid system adapted to be connected to a line extending to said apparatus, a normally active channel for transmitting signal currents from said transmitting means to said hybrid system, a second normally active channel for transmitting signal 'currents from said hybrid system to said receiving means, a voltage divider included in each v of said channels, each of said dividers including a leg serially included in the associated channel and a leg shunting a portion of the associated channel, an electron discharge tube including output electrodes bridged across one leg of the divider included in one of said channels so that the signal current transmission efficiency of said one channel is determined by the impedance across said electrodes, a second electron discharge tube including output electrodes bridged across one leg of the voltage divider included in the V .mission eliiciency of said one channel and substantially to decrease the signal current transmission e'iciency of said other channel, and means controlled in accordance with the amph- Vtude of signal currents traversing said one channel for changing the output electrode imped
  • a transmission system In a transmission system, a, signal current transmission channel, an electron discharge tube including a pair of output electrodes and a control electrode for changing the impedance across said output electrodes, means coupling said output electrodes to said channel so that the transchannel to vary the signal current transmission efficiency of said one channel inversely "in'accordance with the amplitude of the signal input' 8.
  • a signal current transmission channel In a. transmission system, a signal current transmission channel, a voltage divider comprising a leg serially included in said channel and a.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Interconnected Communication Systems, Intercoms, And Interphones (AREA)
  • Amplifiers (AREA)
US290088A 1939-08-14 1939-08-14 Transmission system Expired - Lifetime US2282404A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
BE464852D BE464852A (enrdf_load_stackoverflow) 1939-08-14
US290088A US2282404A (en) 1939-08-14 1939-08-14 Transmission system
GB12372/40A GB541981A (en) 1939-08-14 1940-07-31 Improvements in two-way transmission systems
FR930807D FR930807A (fr) 1939-08-14 1946-07-18 Perfectionnements aux répétiteurs de transmission à deux directions

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US290088A US2282404A (en) 1939-08-14 1939-08-14 Transmission system

Publications (1)

Publication Number Publication Date
US2282404A true US2282404A (en) 1942-05-12

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Application Number Title Priority Date Filing Date
US290088A Expired - Lifetime US2282404A (en) 1939-08-14 1939-08-14 Transmission system

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US (1) US2282404A (enrdf_load_stackoverflow)
BE (1) BE464852A (enrdf_load_stackoverflow)
FR (1) FR930807A (enrdf_load_stackoverflow)
GB (1) GB541981A (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2831922A (en) * 1953-05-06 1958-04-22 Gai Tronics Corp Telephone substation
US2850569A (en) * 1953-09-07 1958-09-02 Defensor A G Electric arrangement for speech transmission in two directions
US3060265A (en) * 1960-01-26 1962-10-23 Itt Conference call circuit

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2831922A (en) * 1953-05-06 1958-04-22 Gai Tronics Corp Telephone substation
US2850569A (en) * 1953-09-07 1958-09-02 Defensor A G Electric arrangement for speech transmission in two directions
US3060265A (en) * 1960-01-26 1962-10-23 Itt Conference call circuit

Also Published As

Publication number Publication date
BE464852A (enrdf_load_stackoverflow)
FR930807A (fr) 1948-02-05
GB541981A (en) 1941-12-19

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