Dolby Laboratories DA20 Panduan Pengguna - Halaman 13
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Halaman Cetak1.5
Single Projector Installations
In single projector installations, the Proj 1 motor start input is normally grounded with a
jumper. Presence of this conection is shown by a continuously illuminated Proj 1 led on
the Cat. No. 611. If this connection is not present, a fault in the digital data will not cause
the system to switch to analog; it will just go silent. For this reason it is very important to
jumper pin 1 to pin 5 on the motor start connector J9 in a single projector system.
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Two Projector Changeover Operation
The DA20 "changes over" between Cat. No.700 Digital Soundheads by switching
between digital data signals at a time in advance of the actual picture changeover. The
data on the film is read by the Digital Soundhead ahead of the picture gate by typically
1-1/2 seconds. A delay circuit in the DA20, set during installation, compensates for this
"early" reading of data. In order for a changeover to be seamless, the switchover to the
incoming digital data must happen "early" as well. The Motor Start signal (a contact
which closes when power is applied to the projector) is used to initiate the digital
changeover. Digital changeover occurs at eight seconds minus the amount of delay set at
installation. Eight seconds is the time between the motor start cue at the end of a reel and
the last picture frame on that reel. If the Digital Soundhead were located at the analog
soundhead position, no fixed delay would be required, and the digital changeover would
happen simultaneously with the picture changeover. Any amount of delay added to the
digital signal to compensate for "early reading" (ahead of the analog soundhead) must be
subtracted from the 8 seconds to get the time that the digital signal must be switched after
the motor start.
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Operation With an Automation System
The DA20 may be used in conjunction with any standard automation system, but the
following guidelines must be followed:
To select Dolby Stereo Digital, format 10 must be selected. If no valid digital data is
present, either due to an analog only print or to problems reading the digital track, the
DA20 Cinema Processor system will automatically switch to format 05, Dolby SR.
When used with a CP45, CP55, CP65, or CP500, the automation system must use
momentary Cinema Processor format select lines. The DA20 senses and controls these
lines to switch between digital and analog as required. If format lines are held
continuously, incorrect operation will result, and this situation will need to be corrected.
When used with a CP200 Cinema Processor, the automation system controls the Cinema
Processor. It, in turn, sends a signal to the DA20 indicating that digital sound is desired.
The DA20 responds with a green LED located on the DA20 front panel indicating that
digital audio has been decoded and is present on its output lines. If valid digital data is
not available, a yellow LED will be on.
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