| 摘要 |
PURPOSE:To reduce the number of comparing means for a display device, by a method wherein a DC level for a plurality of signals is time-divided and fetched in synchronism with a horizontal synchronizing signal, and is compared with a voltage which changes in steps with the passage of a time during a vertical scanning period. CONSTITUTION:An audio signal reaching an input terminal 1 is supplied to a multiplexer 4 via octave-pass filters 21-210 and an attenuator 3, and a spectrum signal is time-divided in turn and fetched by means of a horizontal synchronizing signal from a video display generator 5 for the duration of a horizontal scanning period. The spectrum signal is held in the same level in a comparator 14 for one horizontal scanning period of a picture signal from a comparing voltage generator 6, and is compared with a voltage (o) in which a level changes in steps with the passage of a time for the duration of a vertical scanning period. A comparing output is supplied to a RF modulator 17 via a blanking circuit 15, an attenuator 16, and a diode D2, and after it is overlapped with a chromaticity signal and a chrominance sub-carrier, it is supplied to a picture tube 11 to display a spectrum signal and a full-band signal. |
