GB540454A - Automatic gain control system - Google Patents
Automatic gain control systemInfo
- Publication number
- GB540454A GB540454A GB6850/40A GB685040A GB540454A GB 540454 A GB540454 A GB 540454A GB 6850/40 A GB6850/40 A GB 6850/40A GB 685040 A GB685040 A GB 685040A GB 540454 A GB540454 A GB 540454A
- Authority
- GB
- United Kingdom
- Prior art keywords
- signal
- valve
- negative
- diode
- control
- 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
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/44—Receiver circuitry for the reception of television signals according to analogue transmission standards
- H04N5/52—Automatic gain control
Landscapes
- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Control Of Amplification And Gain Control (AREA)
- Video Image Reproduction Devices For Color Tv Systems (AREA)
Abstract
540,454. Automatic volume control. PHILCO RADIO & TELEVISION CORPORATION. April 16, 1940, No. 6850. Convention date, May 24, 1939. [Class 40 (v)] In a composite signal system employing a signal having components established on opposite sides of a predetermined amplitude level, a signal channel means for deriving a signal from said channel, a gain control valve operable by said described signal, means for causing the effective anode current of said valve to decrease rapidly and abruptly from a substantial value to cut off, means whereby the operating conditions of said valve can be adjusted so that said amplitude level is normally slightly above the cut-off point of the valve, to render the valve fully responsive to one of the said signal components and but slightly responsive to the other component, thereby to obtain an output signal which is substantially independent of variations of the other signal component, and means for applying the output signal to the signal channel to control the gain thereof. Fig. 1 shows the invention applied to a television receiver. The control signal is taken from the LF. output and is applied to the grid of a triode 9 across a leak resistor 10 connected to a source of negative bias 11. The cathode is slightly less negative, being connected to the centre tap of a voltage divider 12, 13. The plate load resistor 16 is connected by a smoothing filter 18, 19 to the anode of a diode 20 from where the A.V.C. voltage is fed over a line 21 to the I.F. amplifier or earlier stage. Until the signal applied to the grid of valve 9 is sufficiently large to cause the plate to go negative, no negative control voltage is developed across condenser 19 but when the plate goes negative diode 20 ceases to conduct, and condenser 19 is charged through resistor 18. When the signal declines condenser 19 discharges until another signal peak occurs to drive the plate of valve 9 negative. Curves are shown to demonstrate that this arrangement gives a control voltage which is large relative to the change in signal amplitude and as applied to a standard television signal serves to maintain the blanking level and the amplitudes of the synchronizing pulses constant. The use of the diode 20 introduces a delay action which may be varied by altering the bias of the diode. Specification 537,856 is referred to.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US275525A US2240601A (en) | 1939-05-24 | 1939-05-24 | Automatic gain control system |
Publications (1)
Publication Number | Publication Date |
---|---|
GB540454A true GB540454A (en) | 1941-10-17 |
Family
ID=23052683
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB6850/40A Expired GB540454A (en) | 1939-05-24 | 1940-04-16 | Automatic gain control system |
Country Status (2)
Country | Link |
---|---|
US (1) | US2240601A (en) |
GB (1) | GB540454A (en) |
Families Citing this family (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2519359A (en) * | 1944-09-29 | 1950-08-22 | Sperry Corp | Automatic volume control |
US2526608A (en) * | 1945-03-27 | 1950-10-17 | Socony Vacuum Oil Co Inc | Gain control system for seismographs |
US2525103A (en) * | 1948-03-11 | 1950-10-10 | Rca Corp | Apparatus for controlling black level shift in television signals |
US2819337A (en) * | 1952-06-14 | 1958-01-07 | Rca Corp | Automatic gain control circuits |
US2908774A (en) * | 1955-09-16 | 1959-10-13 | Hals Per Jahrmann | Cathode-follower for pulse operation |
GB1331779A (en) * | 1970-08-28 | 1973-09-26 | Communications Patents Ltd | Electric signal responsive device |
US4970592A (en) * | 1988-03-03 | 1990-11-13 | Communications Satellite Corporation | Horizontal synchronization, clock synchronization, D.C. restoration and gain control scheme for an analog TV system |
-
1939
- 1939-05-24 US US275525A patent/US2240601A/en not_active Expired - Lifetime
-
1940
- 1940-04-16 GB GB6850/40A patent/GB540454A/en not_active Expired
Also Published As
Publication number | Publication date |
---|---|
US2240601A (en) | 1941-05-06 |
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