3-1
SECTION 3OPERATION3.1 Operating Modes and Applications
The SDU4 has three modes of normal operation: Mono, Stereo and Dolby
Surround.
Mono
The mono mode combines the Lt and Rt input signals into a single channel
and routes it to the Center loudspeaker, if the internal switch S301 is in the
"yes" position. If the internal switch is in the "no" position, the mono sum of
Lt and Rt is sent to the Left and Right loudspeakers at a reduced level,
thereby creating a correct phantom center image.
Stereo
The stereo mode is provided for conventional stereophonic reproduction of
the input Lt and Rt signals. This mode, in effect, provides an electronic
bypass, leaving the input buffers, master level control and line amplifiers in
the signal path.
The position of the internal Center speaker yes/no switch has no effect in
the stereo mode; there is no output from the Center loudspeaker in either
case.
Dolby Surround
The Dolby Surround mode provides full decoding of the two channel input
material using the internal Cat. No. 150 2:4 channel surround decoder
module.
3.2 Detailed Applications
Broadcast
Broadcast applications include evaluation of transmission masters originally
recorded for theatrical release. Additionally, selected television programs
are now being produced using the Dolby Surround encoding format.
Broadcast of feature films originally released with Dolby encoded
soundtracks are commonplace. The stereo audio tracks on the master
videotapes are normally direct transfers of the original Dolby theatrical
release soundtrack, and therefore surround information is included within
the broadcast audio.
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