GB798773A - Improvements in or relating to synchronising circuits for television receivers - Google Patents
Improvements in or relating to synchronising circuits for television receiversInfo
- Publication number
- GB798773A GB798773A GB4859/55A GB485955A GB798773A GB 798773 A GB798773 A GB 798773A GB 4859/55 A GB4859/55 A GB 4859/55A GB 485955 A GB485955 A GB 485955A GB 798773 A GB798773 A GB 798773A
- Authority
- GB
- United Kingdom
- Prior art keywords
- pulses
- circuit
- derived
- valve
- differentiated
- 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
- H04N5/04—Synchronising
- H04N5/12—Devices in which the synchronising signals are only operative if a phase difference occurs between synchronising and synchronised scanning devices, e.g. flywheel synchronising
- H04N5/126—Devices in which the synchronising signals are only operative if a phase difference occurs between synchronising and synchronised scanning devices, e.g. flywheel synchronising whereby the synchronisation signal indirectly commands a frequency generator
Landscapes
- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Synchronizing For Television (AREA)
Abstract
798,773. Automatic synchronizing systems. TELEFUNKEN GES. Feb. 18, 1955 [Feb. 20, 1954], No. 4859/55. Class 38 (4). [Also in Group XL (c)] In a flywheel synchronising system for television receivers, voltage pulses derived by differentiating the rear edges of received linesynchronizing pulses are used for phase comparison with the short flanks of the sawtooth deflection waves. Differentiated pulses may be obtained from the anode circuit of a valve having a C-R or L-R differentiating circuit, the time constant of which is such that the leading differentiated pulse has no effect on the trailing differentiated pulse, or the leading pulse may be removed by a shunt diode or a triode threshold circuit. As shown, Fig. 19, differentiated line synchronizing pulses are derived from a transformer 91 and applied via capacitors 105, 106 to the grid of a phase comparison triode 107 which is gated and whose mutual conductance is periodically increased by flyback pulses applied to its anode from a blocking oscillator timebase generator 119 and to the junction of the capacitors 105, 106, a sawtooth voltage being applied from the line deflection generator 16. A control voltage is thereby derived from the cathode circuit of the valve 107 dependent on the phase relation between the positive-going differentiated pulses applied to the valve 107 and the sawtooth flyback voltage, which after smoothing is applied to the grid of the blocking oscillator 119 to phase lock it. A compensating voltage applied to the cathode circuit of valve 107 from the cathode circuit of valve. 102 allows for the greater duration of conduction during picture flyback. In fig, 4, capacitor 93 and resistor 94 differentiate the input negative-going line synchronizing pulses to a biased. triode 95 so that only pulses due to the rear edges are derived across a transformer 150 in the anode circuit of the valve. Flyback pulses 151 from the deflection generator 16 are also differentiated by the capacitor-resistor circuit 152, 153 to derive the waveform 154 applied to the centre-tap of the transformer secondary. A differential voltage from the two series of superimposed pulses (one shown at 161) is therefore derived from the output of the rectifiers 155, 156 and, after smoothing, applied to phase-lock the blocking oscillator or multi-vibrator time-base generator 14. It is shown that the use of the rear edge of the synchronizing pulse avoids the positional change, due to circuit time constants, of the derived line synchronizing pulses when lines, for some length of time, change from ending in white to ending in black. Specification 753,871 is referred to.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE798773X | 1954-02-20 |
Publications (1)
Publication Number | Publication Date |
---|---|
GB798773A true GB798773A (en) | 1958-07-30 |
Family
ID=6711481
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB4859/55A Expired GB798773A (en) | 1954-02-20 | 1955-02-18 | Improvements in or relating to synchronising circuits for television receivers |
Country Status (1)
Country | Link |
---|---|
GB (1) | GB798773A (en) |
-
1955
- 1955-02-18 GB GB4859/55A patent/GB798773A/en not_active Expired
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