Specifications

This ground loop is created by the normal ground at the DVR or Monitor and
the new ground applied by the lightning arrestors. This will look like black or
translucent bars on the video image. These bars can stand still or move slowly up
the screen. When the bars reach the top of the screen others will appear at the
bottom of the screen to take their place.
Since you cannot remove one of the grounds to eliminate the ground loop it
may be necessary to install ground loop blockers to finish the system. The ground
loop blockers will remove the interfering signals created by the lightning arrestors
and the arrestors will protect the system from lightning strikes. The ground loop
blockers are called GB-60, or GB464 and they are available from FM SYSTEMS,
INC.
Remember, grounding is for electrical shock protection purposes.
Lightning arrestors reduce damage to electronics from lightning. You can’t avoid
equipment damage from a direct hit. Both bonding and grounding conditions must
be met to protect both people and the equipment.
CCTV LINE-LOCK PROBLEMS.
Someone once said, "Timing is everything". The same thing can be said about
Line-Lock CCTV camera installations. The Line-Lock feature is available on most
CCTV cameras, and is used to prevent picture rolling on the monitor during
switching from one camera to another. Picture Roll will cause the loss of vital picture
information in the video recorder and is irritating to view. This article will discuss the
problems encountered by installation and maintenance personnel along with
solutions to save time and make your job more profitable.
The CCTV camera puts out a series of pulses called "Sync" pulses that allow
a video monitor to synchronize the picture on the screen. Special sync pulses called
"Vertical Interval Pulses" tell the monitor to begin a new picture. The Vertical Interval
Pulses from multiple cameras must be synchronized if you wish to switch from one
camera to another without the monitor producing a picture roll. When a roll in the
monitor occurs, the Vertical Interval can be seen as a black horizontal bar that
appears momentarily on the screen.
Lets look at how the Line-Lock system keeps CCTV cameras in synchronism.
To synchronize multiple cameras you must first have a common reference that is all
the cameras must share the same timing information. The term Line-Lock refers to
the 60 cycle AC (alternating current) supplied by the power company.
CCTV TRAINING MANUAL PAGE 16 OF 28