SS0607-8
30 September 1988
a. The older-style cameras would receive pulses directly from the sync
generator. Drive pulses to other pieces of source equipment would then have
to be delayed to time that equipment. This delay could be obtained by using
several hundred feet of coaxial cable or some equivalent relay system using
inductance or capacitance.
b. Cameras are in use today that require sync, blanking, and
subcarrier.
However, horizontal and vertical drive are now virtually
obsolete.
Older cameras (prior to 1978) have no internal timing
adjustments, so it is necessary to adjust the advanced pulse drives to time
the camera.
One way to resolve this timing requirement is to drive the
camera with a source-synchronizing generator. New cameras (after 1978) lock
to color black and have internal timing adjustments available.
2.
Until now, most character generators have required pulse drives and
external adjustment to timing.
This is done by dedicating a source-
synchronizing generator to the character generator.
Newer character
generator models, like other devices, are beginning to lock to color black.
3.
Digital video devices, such as digital effects generators, time base
correctors, and frame synchronizers, work on the basis of storing digital
video data. This allows timing to be easily adjusted and, as such, digital
video devices are inherently able to time internally. Color black locking
is very common.
4.
Nearly
all
production
switchers
require
sync,
blanking,
and
subcarrier. Some switchers have limited adjustment of horizontal (H) delay,
but still require advance pulse drives.
Subcarrier phasing is normally
built in and allows for color timing of the switcher.
Dedication of a
source-synchronizing generator to a switcher will simplify system design.
Some switcher designs now incorporate color black locking.
Learning Event 2:
DESCRIBE THE EQUIPMENT AND PROCEDURES USED FOR TIMING DELAYS
1.
Coaxial (coax) cable is necessary for the proper distribution of
video, pulse, and subcarrier signals. Coax has an inherent delay of up to
1.5 nanoseconds (ns) per foot.
This is cumulative and must be considered
in-system design. Very long runs can introduce significant delay. Coaxial
cable can be used for delay but it should be remembered that coax introduces
frequency response loss that increases with frequency and length.
2.
Distribution amplifiers (DA) introduce delay that must be planned for.
This can vary from 25 to 75 ns depending on the model.
Variable cable
equalization adjustment will also affect electrical delay.
should be adjusted prior to final system timing. Special purpose
11
Previous Page
