The rotation of the drum _A_ carrying the lenses _b_, _b′_, _b″_,
etc., causes the image of the light source _S_ to sweep across the
screen _Y_ in two directions. A complete rotation every sixteenth of
a second is motion picture speed.
]
[Illustration:
Radio Vision hook-up circuits. _A_ is the light cell. The upper
circuit puts a “chopper” frequency onto the radio carrier wave by
the inductive coupling.
The lower diagram shows an intermediate frequency oscillator to be
controlled by a light cell (not shown), the intermediate being put
on the carrier wave.
]