Specifications

If it is a Tape Recorder, old or worn tape will play back fewer "Lines" than
new tape. Even new tape of different types may show variation in the number of
"Lines" played back. Worn Tape Heads will also show fewer "Lines" than new
Tape Heads. It is recommended that this test be performed at regular intervals to
catch Tape Head wear before performance suffers.
After the Monitor and recorder have been proven to display at the desired
quality level, a Camera is chosen that is capable of at least equal "Lines"
capability. Now the entire CCTV system is assembled complete with the
transmission system (whether coaxial cable, twisted pair wires, fiber-optic, or
wireless) to see if the transmission system degrades the overall system
performance.
To perform a picture quality test of the complete CCTV system, temporarily
replace the Camera with the VLTG-800 test generator. Now the test signal must
traverse the transmission system (coaxial cable, twisted wire, fiber-optic, or
wireless) as well as the receiving terminal equipment. The video losses
encountered in the transmission facilities will degrade the number of "Lines"
observable in direct proportion to the length and type of facility.
Now compare the "Lines" observable through the entire system to that
observed on the Monitor alone. If the "Lines" have been significantly reduced
below the performance target because of the losses created by the transmission
facilities, then it is time to consider applying amplifiers and equalizers to the
system to bring it up to performance targets.
Loss of video level and the even much greater loss of high frequency
resolution occurs on coaxial cable and twisted wire (UTP) facilities in direct
proportion to the length and quality of those facilities. Serious loss of quality in
terms of "Lines" can begin to occur in un-equalized transmission facilities as short
as 400 feet or less.
Finally, after the Monitor and Recorder have been proven to display at the
desired quality level, overall tests can be made, including the Transmission
facilities. To do this, temporarily connect the VLTG-800 in the place of the Camera
and observe the number of "Lines" that are clear on the Monitor. If the number of
"Lines" now observable is lower that the desired quality performance level, that
condition can be cured by adding amplifier/equalizers to the transmission facility.
Twisted Pair (UTP) and coaxial cable equalizers can
fully compensate for the
loss of picture level and loss of "Lines of Definition" in cables up to about 4000
feet.
CCTV TRAINING MANUAL PAGE 23 OF 28