Analog CCTV Architecture & Design

The architecture and design of a Analog Closed Circuit Television (CCTV) system is critical and most of the times is done wrong. This can be from lack of knowledge on the system integrators part in learning how to do this properly.

There are some very basic elements in the architecture of these systems are the components involved. We will go through the components for an analog system setup and detail the design.

The analog CCTV system is comprised of six different components that need to be pieced together. Those are Cameras, Lenses, Power Supplies, Cable Types, Recording Device, and Monitors.

Cameras can play an essential part of the architecture and if the wrong type of camera is selected it could mean changing them out which could cost you money. There are many different types of cameras Traditional Box cameras, Bullet, Dome, Pan Tilt Zoom (PTZ), and Covert/Discreet. They have characteristics which include indoor or outdoor, vandal proof / resistant, and day/night. Choosing an indoor dome camera for an outdoor environment will mean disaster. There is also a Wide Dynamic Range (WDR) option within cameras which will allow for light compensation when a camera is placed in front of a glass window or doorway. The WDR function allows the compensation between the exterior and interior light to provide you a clear picture rather then just a silhouette of the individual walking in. So, choosing the appropriate camera is vital in all applications.

The lens of a camera will come into effect when you are trying to acquire and image of a certain area AKA field of view. This field of view is measured upon the cameras Charged Coupled Device (CCD) which is the cameras image sensor and can range from ¼” to ½” in the CCTV cameras. The range means the bigger you are in CCD the bigger the field of view in horizontal and vertical degrees. This coupled with the lens, which come in two different flavors Fixed and Vari-Focal will give you desired field of view. The fixed lens which is a little lower in price is beginning to see its end of life in the security cameras as more people are switching to eh flexibility offered in the vari-focal. The vari-focal offers the ability to manipulate (manually) the lens from wide angle to tele-focal. Some common fixed lens sizes are 2.6mm, 3mm, 6mm, 8mm, and 16mm and for the vari-focal are 2.8 – 10mm, 3 – 9mm, 4 – 8mm, and 5 – 50mm. What this allows the installer to do is widen the field of view or tighten it depending upon the end users request. This is much cheaper to do then actually moving the camera when a fixed lens is in the camera because it can be laborious.

Then comes the power supply which can mean all the difference if you don’t want to blow cameras while installing them. There are essentially two different types of requirements when it comes to power for surveillance cameras which are 12 VDC and 24 VAC. Some camera manufacturer will make a dual voltage camera with auto sensing so it can be 12VDC or 24VAC. The days of using the big bulky transformers are gone; the new trend is using a distributed power supply. This power supply can give you several different outputs from 4 to 32. This means you have all your power cables coming into one box, which provides power to all the cameras connected to the power supply. They also are now protected via a fuse or breaker in the case of a power surge which reduces the risk of damage to the camera. They are usually wall or rack mounted and can be very beneficial to a “clean” install.

There are several ways of cabling for CCTV the most common is the use of the Coaxial Cable which is zipped together with a power cable 2 conductor 18 gauge or known as 18/2. This cable is called a Siamese cable and zips apart for video and power on the camera end and on the recording end. The other way is to use a Category 5 (CAT5) or better using “baluns” or transceivers as they are known. With this method you can use a 4 pairs of the CAT5 cable for transmission of video up to 5000ft with the correct hardware on both the camera end and the head end. This method can also give you power over that same cable (not to be confused with Power over Ethernet (PoE) which we will speak about in later discussions. The final way of cabling is the use of Fiber Optic cable which can provide transmission for many miles and help protect against lightning and surges.

Recording is the most integral part of the system design and in the old days this was done by having a multiplexer or MUX receiving all the video feeds and then connecting a time-lapse vcr. The new technology is the use of Digital Video Recorders (DVR’s) which replace both the equipments with one that does more functions including the ability to remote view. The latter is also now being replaced with Network Video Recorders (NVR’s) which provide more scalability.

The final component is the monitor! Having the right monitor makes all the difference and monitor come in Cathode Ray Tube (CRT) or Liquid Crystal Display (LCD). CRT’s provide the best quality picture on CCTV systems, but are big and bulky. LCD’s are more space saving but if it is not a high resolution monitor then the images may not be as clear. Having a low resolution monitor with a high resolution camera defeats the purpose of a good quality video image. Choosing the right monitor can make or break your system.

In conclusion, as you can see there many different components that makes up CCTV architecture and can be very costly in the long run if it is not done correctly from the beginning. So, let’s make sure that if planning out a CCTV design to check back for further design help.

See you on the next topic!

Kal