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INSTALLATION
pulses usually come at a rate of 10 pulses per film frame. The 4025TR can
also accommodate tach rates of 1, 2 or 5 pulses per frame. For best
results use the highest biphase rate possible. Use the BIPHASE RATE
menu item of the Toolbox Hardware menu to adjust the 4025TR to the
correct biphase rate. (See section 3.6.3) Correct connections will result in
EDGE numbers that increment and decrement when the telecine moves
forward and reverse respectively. In the event that the 4025TR counts in
the reverse direction when the telecine is in forward play, reverse the two
biphase connections to the 4025TR.
To minimize the effects of cross coupling and noise on the biphase signals,
which can affect the counting reliability of the 4025TR, you use a cable,
which provides separate shields for each phase of the biphase signal.
2.11.2 Cintel Film Frame Pulse
In addition to the biphase connections, a film frame pulse is required. This
active low pulse occurs when a new film frame starts in the video output,
while the telecine is in normal play speed. The 4025TR uses the film frame
pulse to lock its timecode output to the correct telecine pulldown sequence
during the transfer.
Some telecines, such as Cintel MKIIIC Digiscan 3 models, continue the
frame pulse in an unbroken sequence even when they are in shuttle
modes. When used with these telecines, the 4025TR can be configured for
AUTO rate detect. Changes in transfer rates by the telecine operator are
automatically detected when the telecine is in still. (See sections 3.4.4 or
3.10.9 for information on how to select auto rate detect mode). Other
telecines, such as Cintel 4:2:2 Digiscan 4 and URSA models do not
maintain coherent film frame pulse sequences in shuttle modes. When
used with these telecines, the 4025TR must be manually set to the correct
transfer rate to accurately track the film/timecode relationship.
The actual DC voltage level of the film frame pulse is not critical as long as
a 1 volt peak to peak minimum signal is applied. The film frame pulse is
sampled once per video field approximately mid-field.
Figure 2-10 shows the timing requirements for the Cintel frame pulse. The
frame pulse must be low at the trailing end of vertical sync and return high
again before the end of the field.
Model 4025TR Film Footage Encoder Manual
Page 2-16
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