US2280672A - Automatic gain control - Google Patents

Automatic gain control Download PDF

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Publication number
US2280672A
US2280672A US366468A US36646840A US2280672A US 2280672 A US2280672 A US 2280672A US 366468 A US366468 A US 366468A US 36646840 A US36646840 A US 36646840A US 2280672 A US2280672 A US 2280672A
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United States
Prior art keywords
gain
meter
line
relay
amplifier
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US366468A
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English (en)
Inventor
Terroni Teseo Bruno Dante
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Automatic Telephone and Electric Co Ltd
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Automatic Telephone and Electric Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Automatic Telephone and Electric Co Ltd filed Critical Automatic Telephone and Electric Co Ltd
Application granted granted Critical
Publication of US2280672A publication Critical patent/US2280672A/en
Anticipated expiration legal-status Critical
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M3/00—Automatic or semi-automatic exchanges
    • H04M3/40—Applications of speech amplifiers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/04—Control of transmission; Equalising

Definitions

  • the present invention is concerned with improvements in or relatingto carrier telephone and like carrier signalling systems, and is more particularly concerned with automatic gain con- 1 trol arrangements for use therein.
  • thermionic repeaters In systems of the above type it is the usu practice to employ at intermediate points and possibly also at terminal points, thermionic repeaters by means of which the received speech and/or signal energy is amplified before it ispassed on along the line.
  • the gain of the various amplifiers can be set so that in spite of the line attenuation the received energy will be of the same value as the input energy at-the transmitting end.
  • the amplitude of the current at the point of reception or gain control serving to adjust the gain control in inverse ratio so as to maintain the strength of output currentequal or in some other definite relation to the input current with varying line conditions.
  • the current is measured by means of a meter at each point at which automatic gain control is to be provided, the reading of the meter being scanned by a light ray and the arrangements are such that in accordance with the reading of the meter a number of impulses are generated which step a switch-to a position connecting with one of a number of tappings on a gain control rheostat in such manner that the output energy transmitted from each amplifier station will remain at the pre-set value irrespective of variations in the input energy received thereat.
  • the scanning of the meter reading is arranged to be made at a slow speed and two setting switches are provided which respond alternatively to the series of pulses representative :of the meter reading, a switch after having been set maintaining its position until the second switch has been set by thev next series of impulses and then restoring to normal in readiness for afurther series of impulses and so on.
  • Fig. 1 shows schematically sumcient of the meter circuits and the gain control circuits to enable the invention to be readily understood
  • Fig. 2 shows a known manner of associating the meter with the thermionic valve by which the gain control circuits are controlled and is substantially identical with the drawing of British specification No.
  • a current having the frequency allotted to the pilot channel when received over the line conductors l0 and I 1 passes through a filter F which is tuned thereto and causesa heavily damped meter movement RM such as that of a direct current ammeter in the anode circuit .of' a suitable detector valve D. which movement is shunted by the condenser 12- to take up a reading corresponding to the amplitude of the received pilot frequency current.
  • a current having the frequency allotted to the pilot channel when received over the line conductors l0 and I 1 passes through a filter F which is tuned thereto and causesa heavily damped meter movement RM such as that of a direct current ammeter in the anode circuit .of' a suitable detector valve D. which movement is shunted by the condenser 12- to take up a reading corresponding to the amplitude of the received pilot frequency current.
  • the frequency of pilot channel will lie in the unused portion of the transmitter carrier frequency range, and the amplitude of the energy transmitted at the sending end
  • meter RM illustrated in more detail in Fig. 2, this will be of the so-called "photo-telemetering type, the construction of which is known to those versed in the remote supervisory control art and the general form and operation of which is disclosed in our prior British specifications Nos. 441,881, 441,999 and 460,187.
  • thermionic valve V which may be a vacuum tube of I the trigger gas discharge type and in the anode circuit of which is connected a relay IMP.
  • Relay IMP in responding to one set of impulses steps a switch which will be designated as switch A to a corresponding position as a result of which a suitable tapping is selected on the gain control rheostat l6 via wiper and bank A4.
  • a switch which will be designated as switch B On receipt of a second set of impulses corresponding to the next scanning operation, a switch which will be designated as switch B is set to a position corresponding thereto and switch A, is honed and prepared to receive the next series of impulses.
  • the switches A and B are of the electromagnetically operated reverse drive type, and are assumed for the purpose of the invention to have six positions, although of course in practice ten or more positions will be the more usual, in order that a finer adjustment of the amount of gain may be effected.
  • the deflection of the meter RM will be approximately proportional to the strength of the pilot frequency current as measured in decibels above or below standard.
  • relay COA is short-circuited by the positive extended over armature cobl and releases so that the gain control is handed over to wiper and bank 134 over the normally closed springs associated with armature coat.
  • relay COY is released and in turn releases relay RB.
  • relay COX is operated, locks and operates relay RA in order to remove the short circuit from relay COA in readiness for the third series of impulses.
  • relay A In response to the third series of impulses relay A is once again set to a position corresponding to the position of the meter pointer and the operation will thereupon continue in the manner already described.
  • Circumstances leading to variation in the level of the received pilot frequency also bring about the same variations in the received carrier frequency level at an amplifier point in a connection, and at this point the apparatus according to the invention ensures that a corresponding inverse variation is made to the gain of the amplifier so that the output level is maintained constant irrespective of variations in the input level thereto.
  • a line a filter connected to said line designed to pass currents having a frequency or frequencies close to but outside the frequency band of the carrler-waves, variably-responsive means controlled by current passing from the line through said filter, an amplifier connected to said line independently of said filter by which the carrierwaves are amplified, gain-controlling means for determining the gain of said amplifier, a second gain-controlling means for determining the gain of said amplifier and cyclically operated switching means for placing one gain-controlling means under the control of said variably-responsive means in inverse relationship to the strength of current flowing through said filter while the gain of said amplifier is controlled solely by said second gain controlling means.
  • a carrier-wave signalling system a line, a filter connected to said line designed to .pass currents having a frequency or frequencies close to but outside the frequency band of the carrierwaves, variably-responsive means controlled by current passing from the line through said filter, an amplifier connected to said line independently of said filter by which the carrier-waves are amplified, gain-controlling means for determining the gain of said amplifier, a second gain-controlling means for determining the gain of said amplifier, said gain-controlling means each including a device adapted to be variably set by said variably-responsive means and means for alternately placing one device solely under the control of said variably-responsive-means while the 3.
  • a carrier-wave signalling system a line, a filter connected to said line designed to pass currents having a frequency or frequencies close to but outside the frequency band of the carrierwaves, a meter controlled by current passing from the line through said filter, an amplifier connected to said line independently of said filter by which the carrier-waves are amplified, a comb having teeth a variable numberof which is exposed by said meter according to the current flowing through it, a light sensitive element, means for causing a ray of light to scan said teeth cyclically and cause the light sensitive element to generate pulses corresponding in number tothe number of teeth exposed, a step-by-step switch including means for determining the gain of said amplifier arranged to be set by said pulses, a second step-by-step switch including means for determining the gain of said amplifier also arranged to be set by pulses from said scanning means, switching means whereby one step-bystep switch is alone connected up to control the gain of the amplifier while the other is being reset by pulses from said scanning means and controlling means responsive to the successive series of
  • a line a filter connected to said line designed to pass cur-- rents having a frequency or frequencies close to but outside the frequency band of the carrier waves, a meter variably responsive to the strength of current received from the line' through the filter, an amplifier connected to said line independently of said filter by which the carrier waves are amplified, means for causing a light ray to periodically traverse the indicating face of said meter, means controlled by said meter through the medium of said light ray to cause the generation of impulses of current, a
  • step-by-step switching device controlled by said impulse generating means to take up a position corresponding to the reading of said meter, and gain controlling means controlled by said step-bystep switching device.
  • a line a filter connected to said line designed to pass currents having a frequency or frequencies close to but outside the frequency band of the carrier waves, a meter variably responsive to the strength of current received from the line through the filter, an amplifier connected to said line independently of said filter by which the carrier waves are amplified, means for causing alight ray to periodicallytraverse the indicating face of said meter, means controlled by said meter through the medium of said light ray to cause the generation of impulses of current, two step-by-step switching devices, means for causing said switching devices to be controlled alternately by said impulse generating means so that one is restored to normal and reset while the other remains operated, gain controlling means controlled by each switching device and switching means whereby the operated switching device is alone efiective in determining the gain of said circuit;
  • a line a filter connected to said line designed to pass currents having a frequency orfrequencies close to but outside the frequency band of the carrier waves, a meter variably responsive to the strength of current received from the line through the filter, an amplifier connected to said line independently of said filter by which the carrier waves are amplified, means for causing a light ray toperiodically traverse the indicating face of said meter, progressively-operated means controlled by said meter through the medium of said light rays to take up a position corresponding to the reading of said meter and gain-controlling means controlled by said progressively-operated means.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Structure Of Telephone Exchanges (AREA)
  • Arrangements For Transmission Of Measured Signals (AREA)
US366468A 1939-12-11 1940-11-20 Automatic gain control Expired - Lifetime US2280672A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB31923/39A GB535124A (en) 1939-12-11 1939-12-11 Improvements in or relating to carrier telephone and signalling systems

Publications (1)

Publication Number Publication Date
US2280672A true US2280672A (en) 1942-04-21

Family

ID=10330402

Family Applications (1)

Application Number Title Priority Date Filing Date
US366468A Expired - Lifetime US2280672A (en) 1939-12-11 1940-11-20 Automatic gain control

Country Status (5)

Country Link
US (1) US2280672A (fr)
BE (1) BE465689A (fr)
FR (1) FR927296A (fr)
GB (1) GB535124A (fr)
NL (1) NL75995C (fr)

Also Published As

Publication number Publication date
FR927296A (fr) 1947-10-24
GB535124A (en) 1941-03-28
NL75995C (fr)
BE465689A (fr)

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