13246_CAI_Feedback_Mar2018_COMPLETE_v1

Closed Circuit TV (CCTV) facilities can be incorporated into MATV and IRS systems in order to provide additional services. These could range from a single door camera on a block of flats (distributed as an analogue UHF TV channel or an additional digital TV multiplex) to a multi-camera installation in a large house. This article describes the technical parameters to be considered when designing a CCTV system and typical applications for services of this type. CCTV is used to generate signals from a video camera, for relay to another location, usually for surveillance applications. Instead of being broadcast, the signals are distributed on coaxial or data cables, or via the internet. For industrial applications, CCTV cameras can monitor processes in hazardous areas. Digital video recording can provide for the monitoring of images either on a one-off basis, or over a long period of time. Most CCTV cameras now incorporate light sensitive image sensors known as Charge Coupled Devices (CCD). The sensitive area comprises a large number of individual picture elements, or pixels. The image is focused through a lens onto the chip surface which causes a charge to build up in each pixel that is proportional to the amount of light falling on it. The lens produces an image in the shape of a circle. CCD devices normally have an aspect ratio of 4:3 and the sensor sizes are shown alongside. The most popular size is 1/3”. The aperture of a lens determines the amount of light falling on the image sensor, and is quoted as an “f” number or f-stop. A lens with a low f stop (such as f1.4) focuses the light onto the CCD chip. A lens with twice as high an f stop (f2.8) will pass CCTV for Profit Robert A Calaz C Eng Charge Coupled Devices (CCD) 42 CAI Feedback Spring 2018