Volume control in movie theaters

The power video-audio shaft replay's system with one, the sound shaft sound rail and multiple audio shaft sound rail. Adjusting the obtaining of the sound rail and a volume expanded. The volume expanded comprises a defined is provided with a range in a large in parallel, front; the number of track substantially provided with a first relationship of volume control arranged; and obtaining of the sound rail substantially provided with a second relationship of volume control arranged, the second a one ends are less than the volume control is 0.01-0.99 of the first is; the number of track front of reducer is substantially of invariable, and obtaining of the sound rail reduced, or a track for obtaining of the gain ratio sound rail front of reducer is reduced gently.