Specifications

7-7
7.9 Cat. No. 673
Error Rate Display
Following powerup, with no film running, the seven-segment display on the Cat.
No. 673 will display a “-” indicating no data on which to display error rate. With
film running, the display will show the error rate of the film on a scale of 0-8 with
intermediate values indicated by the right hand decimal point
(0,0.,1,1.,2,2.,3,3.,4,4.5,5.,6,6.,7,7.,8,) where 0 is the lowest and 8 is the highest.
The display shows “F.” when an uncorrectable block of data is being processed.
See Section 8.2 for further details.
Rotary Switch
This switch should always be set to position 0 for normal operation. It is used to
determine internal software revision levels when servicing the digital sub-system.
7.10 Projector Changeover / Motor Run Indicators
The V1 and V2 indications on the CP500 front panel screen indicate the status of
the video inputs from the Cat. No. 700 Digital Soundhead. Two LEDs on the Cat.
No. 670 card also indicate this status. The M1 and M2 indications show which
projector motor(s) are running. The motor running signals are used in the timing of
changeovers in a two projector system.
The CP500 “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 CP500, 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 eight seconds to get the time that the digital signal
must be switched after the motor start.
7.11 Format Control
When Format 10 Dolby Digital is selected, the audio output terminals of the CP500
will carry decoded digital audio when valid digital data is being read by the
soundhead. When this is not possible (for example, playing an analog only print) the
output of the CP500 will be analog audio in Format 05 (Dolby SR).
The CP500 uses very sophisticated error correction techniques to allow the data to
be read perfectly, even in the presence of heavy scratching and dirt. As with any