Specifications

In commercial buildings the utility power is Three Phase, that is three separate
60 cycle lines whose phase is 120 degrees apart. Moving the power line that your
camera is on to a different phase will throw off the timing and require a re-
adjustment of the phase control on the camera.
If monitor personnel complain about picture roll, a fast check of timing can be
made. Go to the monitor station and connect one camera as a reference to the VTM
or oscilloscope and then connect each camera one at a time to make the
measurement. The timing should be zero +/- 3 Video Lines or Sync Pulses. A roll
can be noticed if the difference between cameras is more than a few lines. As the
line difference between cameras increase so does the noticeable roll. If you
measure a camera and the readings seem to change, that indicates the camera is
not Line-Locked. The solution is to select the Line-Lock feature on the camera or
replace it with one that has Line-Lock.
A clear understanding of how the Line-Lock system works combined with a
way of measuring the Phase of each camera will let you set them quickly and
correctly with confidence.
VTM
VIDEO TIMING METER
CCTV TRAINING MANUAL PAGE 18 OF 28