| 摘要 |
<p>1,159,002. Wired boadcasting; colour television. COMMUNICATIONS PATENTS Ltd. 30 March, 1967 [30 March, 1966], No. 13992/66. Headings H4F and H4R. In a colour television wired distribution system the signal fed to the system comprises a modulated carrier brightness information together with a suppressed carrier colour information signal in respect of two colour information signals and a pilot signal of a frequency equal to the frequency of the suppressed carrier and which is modulated by one colour information component. At the receiver one colour component is derived by envelope detection of the pilot signal and the other by synchronous detection of the colour signal using a reinserted carrier derived from the pilot signal. The transmitter 1 comprises a receiver 16 of broadcast signals of a "PAL" system from which the brightness signal and suppressed carrier colour signals are applied to a modulator 20 to modulate a carrier of about 10.5 Mc/s from oscillator 21. The lower sideband is selected by vestigial sideband filter 23 and applied via mixer 24 to the lines 2 and 3. Colour bursts from the receiver are applied to synchronism oscillator 25 at the frequency of the original suppressed carrier of the colour signal, 4.43 Mc/s, which is modulated by one colour component in modulator 27 before being applied to the lines 2 and 3 via mixer 24. At the receiver 6 the brightness component is selected by filter 31 amplified by amplifier 32 and detected in envelope detector 33, from which the brightness signal is fed out over line 34 while the colour signals modulated on the subcarrier are fed to demodulator 36 via filter 35. The pilot signal, modulated by one colour component, is selected by filter 38 amplified and demodulated at 40 to provide one colour component on line 41, the pilot is also passed through a narrow band filter 44, selecting only the carrier, to provide a carrier for demodulating the other colour component in modulator 36, the phase of the carrier being reversed on alternate lines in phase switch 47, controlled by the colour recognition device 37, to demodulate the appropriate colour component from the colour information sub-carrier wave.</p> |
