Specifications

If you set the iris for more than 100 I.R.E. units, the picture can be washed out
causing loss of picture definition. Some cameras can be set to 120 I.R.E. units, but it
should be noted that the standard is 100 I.R.E. units and in any case all cameras in
the system should be set to the same level of white. This will ensure that the white
portion of the picture will be the same brightness when a monitor is switched
between them.
PEAK TO PEAK MEASUREMENT OF VIDEO.
A quick measurement of the peak to peak video signal will re-assure you that
the CCTV camera is putting out the right level. The standard level is 140 I.R.E. units.
COLOR CAMERAS AND COLOR BURST.
More color cameras are being used in CCTV installations. The color camera
adds a chromanance component (color information) to the signal, also known as
Chroma. This Chroma signal operates at 3.58 Mega-Hertz. The standard level for
the Chroma is 40 I.R.E. units. When the chroma level is low, the colors will be dull. If
this level is too low, the color monitor will turn its color receiver off causing a Black
and White only picture. This condition also indicates a loss of picture detail. You can
see this effect on long cable runs. The solution is to install a video equalizer in the
line and adjust the color burst back to 40 I.R.E. units. If the Chroma signal is too high
the picture will display color flaring and reduction of detail at the edge of the color
flare.
VERTICAL INTERVAL, ITS MANY USES.
The Vertical Interval (V.I.) is the part of the video signal that tells the monitor to
start drawing a new screen. It is made up of special SYNC pulses with no picture
elements. The standard level for these SYNC pulses are 40 I.R.E. units. All video
SYNC pulses should be 40 I.R.E. units. The Vertical Interval is a very useful place to
put alarm and control signals. Some manufacturers make equipment for pan and tilt
camera control, alarm contact information, and data transmission that is inserted into
the V.I. signal and sent up or down the cable.
TERMINATION, THE END OF THE LINE.
A termination for video is a 75 Ohm resistor placed at the end of any video
cable to prevent signal reflections that cause ghosting or multiple images on the
monitor. Some CCTV equipment have built-in terminations some of which are switch
able. If you are using this equipment in series, you must switch off all Terminations
except the termination at the last piece of equipment in the cable run.
CCTV TRAINING MANUAL PAGE 2 OF 28