| 摘要 |
<p>This invention relates to a modulator circuit (2) for a video system such as a VCR. The modulator circuit (2) is selectably operable in any one of a plurality of modes of operation in order to comply with the operating standard of the video system. The modulator circuit comprises oscillator means (4, 10) for generating a carrier signal having a selectably variable frequency, and modulating means (3) coupled to receive the carrier signal and having an audio input (24) for receiving an audio signal and a video input (26) for receiving a video signal, the modulating means using the video and audio signals to generate a modulated output signal on the carrier signal, the generation of the modulated output signal depending on selectably variable operating parameters of the modulating means. The modulator circuit further comprises control means (5, 6, 20) coupled to the oscillator means (4, 10) and to the modulating means (3), for receiving a mode select signal (SCL, SDA) and for selecting the frequency of the carrier signal and for selecting predetermined values for the variable operating parameters of the modulating means in dependence on the mode select signal whereby the modulated output signal is generated in accordance with one of the plurality of modes of operation.</p> |
