Image intensified camera:
is a type of camera coupled with an image intensified tube which generates additional photons. This tube allows the camera to be used in low light areas.

Image intensifier:
is a device which intensifies light by using light sensitive phosphor screens. It is used to improve camera performance under low light conditions.

Impedance:
is the input and output characteristic of any electrical system and is measured in ohms. For maximum signal transfer, the input and output impedance should be the same. CCTV systems have a 75 ohm impedance.

Incandescent light:
is a type of artificial light source invented by Thomas Eddison in 1862. It has a good spectral response but low life and efficiency.

Index of refraction:
is a ratio between the angle of incidence to the angle of refraction of light. It depends upon the density of a medium. A denser medium will have a higher index of refraction and will also bend the light more.

Infrared detector:
is a type of alarm which works on the principle of infrared light to detect movement in a zone

Infrared illuminator:
is a type of light source which emits light in the infrared frequency range.

Infrared link:
is a type of transmission medium in which video, data or audio are modulated with infrared light and then transmitted into air to a receiver in a remote location.

Infrared radiation:
is electromagnetic radiation with a wavelength of more than 750 nanometers. It is not visible to the human eye.

Interference:
is external energy which interferes with an electrical signal causing picture distortions.

Interlacing:
is the process of combining even and odd fields to form a frame.

Interline transfer chip:
is a type of chip used in most of the current CCTV cameras as the charge read out method is more efficient than a frame transfer CCD chip . Vertical streaking and small pixel size are some of the shortcomings.

Iris:
is a part of a lens that can be adjusted to vary the amount of light passing through the lens and falling on the CCD chip.

Iris plug:
is a type of connector which connects the camera to an auto iris lens to provide power to the iris motor and to send the video signal which controls the iris opening.

ISDN Integrated Services Digital Network:
is a type of telephone network which accepts digital signals.