How CCTV Works

CCTV stands for Closed Circuit TV. CCTV uses one or more video cameras to transmit video images and sometimes audio images to a monitor, set of monitors or video recorder. The difference between CCTV and standard TV is that standard TV openly broadcasts signals to the public. CCTV is not openly transmitted to the public. CCTV uses either wireless transmission or a wired transmission to send the broadcast from the video cameras to the monitor(s) or recording device. Most CCTV systems are used for surveillance which can include security monitoring, spying or for safety monitoring purposes.

CCTV Cameras
CCTV systems have become extremely popular over the last few decades as the technology has improved and become more affordable. The majority of CCTV cameras in use today are usually for surveillance and security purposes. You can find CCTV systems in almost every bank, casino, malls and large department stores. In fact, CCTV systems have become so affordable, most smaller mom and pop stores also have CCTV systems in their stores for security purposes.

Types of CCTV Cameras
There are many types of CCTV cameras, they can be categorized by the types of images they are able to capture, the amount of frames they can take per minute, the type of connection to the monitor or video recording device, whether they are able to move position, and special functions they can provide.

Types of Images: CCTV cameras generally take both black and white or color video images. In addition, many CCTV cameras can even have night vision capabilities which allow a CCTV camera to view and record low light images using special technology.

Frames per Second: Frames per second means the amounts of full frames that a video camera captures and sends to a recording device or monitor per second. While most CCTV camera systems are easily able to capture 30 or more frames per second (30 fps is considered real time), the amount of video tape or digital storage would be enormous to record every moment of everyday. For most stores, speeds of 1 to 6 frames per second are more than enough to catch and record a perpetrator committing a crime.

Pan Tilt Zoom (PTZ) Cameras: These types of CCTV cameras allow a person controlling the surveillance of an area to move the camera remotely, usually with an RF or wired controller. Most moveable cameras allow the person monitoring it to move the camera from right to left (pan), up and down (tilt) and from a tight angle to a wide angle (close up zoom).

Cameras with Special Accessories: Certain CCTV cameras have special functions which are made for specialty uses. For instance, there are extremely small surveillance cameras that are used for spying (Nanny Cams), there are cameras that are made for night viewing, cameras that are vandal resistant and cameras that are specifically made for indoor or outdoor uses.

Wired Vs. Wireless Connection
There are two main types of connections for CCTV cameras to the monitor or recording device, they consist of either a fixed cable or a wireless connection.

Fixed Cable Connection
Fixed cable connection means that your camera will be physically connected to your monitor or recording device via a cable. Usually coaxial cables are used, most of the time they are similar to your normal home TV cables. Lengths come in 25, 35, 50, 100 or 500 feet. As the distance increases, you may see degradation in signal quality. For distances longer than 100 or 200 feet, you can purchase higher quality coaxial cables such as RG59 coaxial cable for distances up to 600 feet and for distances more than 600 feet, but less than 2,000 feet, you can purchase CAT5 cable.

Wireless Connection
Most wireless CCTV cameras use the 2.4 Gigahertz frequencies to transmit their video images to a monitor or DVR (digital video recorder). Usually, frequencies can be slightly changed to have more than one group of cameras in a specific space. Wireless CCTV cameras used a this frequency can easily transmit through most walls and obstacles; however each individual location will have its own operating limits. Expect most wireless CCTV cameras to send data to a range of about 200 feet, however many will more likely work well when transmitting less than 150 feet. A clear line of sight transmission will always work the best

Obviously a wireless connection allows you greater freedom to place your CCTV camera almost anywhere. While wireless CCTV cameras transmit their video images to a digital video recorder or monitor, many of these types of cameras must be plugged into an electrical outlet. There is however some CCTV cameras that are battery operated.

Tape vs. Digital Video Recorders
There are two main ways to record video images that your CCTV cameras capture; they are analog tape and digital video recorders. The vast majority of analog video recorders use VCR tapes and either standard VCR's to record the images or special security time-lapse VCR's to record images for a longer period of time.

VCR Tape Recorder
A tape recorder such as a security-time lapse VCR can record CCTV camera images in either black and white or color for either 2,4, 6, 8, etc all the way up to 960 hours which is 40 complete days. The determining factor is how many frames per second you intend to record and how many cameras you have hooked up to your VCR for recording. For instance, if you record 30 frames per second (real time video), you will only be able to get a few hours of video captured on your recorder. If you record one frame per second or less, you can record for dozens of hours before the video tape is full. VCR's are very practical, very reliable and extremely affordable. Expect to pay only a few hundred dollars for a security VCR.

Digital Video Recorders
There are two types of DVR's (Digital Video Recorders). They are either stand alone devices or hard drives that are connected to a computer system. DVR's work similar to VCR's except the images they capture from the CCTV camera is digital. The amount of digital images you can capture on a DVR is determined by a few factors including the frames per second recorded, the amount of cameras hooked up to the DVR device, the resolution that the DVR saves the images at and the video compression used (e.g. MPEG4). For a common set up, where you have 4 cameras shooting at 30 fps and you use an image resolution of 320 X 240, each camera only records when motion is on, and you use MPEG4 compression, you should be able fill up a 20 to 25 GB hard drive in about 80 hours.