Designing of a CCTV System

Designing a CCTV System

Design Requirements

Before any camera, lens, cable or monitor is selected for a CCTV application, a designer must ask three basic questions:

What is the system's function — what is it being designed to accomplish, and will the system be integrated into other systems, i.e. access control system?

Who will manage the system and how?

Is the system new, or is it an upgrade (retrofit) of an existing system?

We will address each of these below.

1. System Function

2. System Management

3. Designing a CCTV System

System Function

Its depends some things like, "depending on the specific purpose of the CCTV system."Determining that purpose is a crucial component of the initial phase of designing any CCTV system.

There's a familiar saying among designers: Form follows function — that is, the form something takes is shaped by its purpose and usage. This form of a CCTV system —

the specific camera and lenses selected,

the mounts and enclosures,

the transmission mediums used,

the monitors, switching devices and recorders

 — all depends on the system's function. In the world of CCTV security systems, there are three basic functions, based upon what the customer wants to see:

detection (alert operator that something is happening)

recognition (allow operator to determine what is happening)

identification (show operator who is involved)

As you can see, there is a priority to these three functions. Detection is the least demanding, recognition is more demanding, and identification places the most demands on the system and the operators. It is not surprising, then, that the design criteria are similarly prioritized. In systems (or subsystems) with detection as the primary focus, there are low design criteria, that is, the demands on the equipment are not as great. Recognition is said to have medium design criteria.

Identification — seeing someone "up close and personal" — requires high design criteria.

System Function

Suppose a designer is planning a CCTV installation at a bank. Security personnel must be able to observe several areas, among them: the entrance, the lobby area, and the teller windows. At the entrance, operators simply want to know that someone is coming into the building (detection). For the purposes of this example, a camera with a fixed focal length lens viewable on a monitor is all that is needed (low design criteria). Once in the lobby area, the operators will want to determine where the subjects are, and what they are doing (recognition). A camera equipped with a remote positioning device and medium range zoom lens is required (medium designer criteria).

Finally, at the teller's windows, it is essential for security personnel to positively identify the subjects (identification). Here the requirement is for an overt, in plain view subsystem which includes a lens with high magnification, attached to a camera with remote control, carefully positioned to afford a uninterrupted view of the subject in even, adequate lighting (high design criteria).

(Note: the Federal Bank Security Act requires teller windows to have a fixed camera, in plain view that captures the teller and person at the teller window.)

In addition to the items presented in the example, the design criteria will evolve to include specifications for monitors. A small monochrome monitor may be sufficient for detection, but a large color monitor with good resolution may be the ideal for identification.

System Management

As a designer begins the task of planning a CCTV system, several policy and personnel issues come into play. Asking the right questions (and getting the right answers) as well as guiding the customer, will help identify the policies and personnel requirements for the system which, in turn, helps define system parameters.

These questions include:

Who will operate the system?

What are the criteria for controlling the system?

What are the recording criteria?

Why are they recordings being made?

How long will the recordings are archived?

What do you want to see and for what purpose?

What limitations do you have, legal and financial?

The answers to the above questions can ensure the recommended CCTV system meets important operating criteria for the customer.

Who will operate the system: Will the operators be direct company-hired personnel or contractor-supplied?

Historically, contractor personnel tend to change more often than company staff members. Experience suggests that company personnel — with greater longevity on the job — can generally handle more complexity in a system than contract workers.

The response to the first questions impacts on the answer to the second question: what are the criteria for controlling the system? CCTV system controls can be fully automatic (computer based operation with programmed sequencing of camera activity, etc.); completely operator-controlled (manual switching, directing outputs, etc.); or a combination of the two. The skill levels of operators may suggest the optimum level of automation for the system.

Now we shift to policy issues. What are the recording criteria? For example, is real time recording of event critical? How about time-lapse recording? Will video be multiplexed? Do you need a demultiplexer for individual camera viewing? If you signal is exposed to potential outside interception, do you want the signal to be recorded to be encoded and then decoded for playback control? Is there a requirement to store images on computer disk as well as video tape?

Why are the recordings being made? Are images being stored simply for administrative purposes — for use by company personnel only? Or will the stored images possibly be used as evidence in possibly litigation?

Finally, how long will the recordings are archived? Long term archiving suggests the need for a storage area which has environmental controls to preserve the tape (as well as space enough to contain the volume of tapes accumulated over the years). Answers to these questions will impact on the type of equipment selected and even the basic design of the system infrastructure.

Designing a CCTV System

New Construction or Retrofit:

Designing a CCTV system can be a lot like house construction. It is often easier to design and proceed with all new construction instead of integrating new components into existing systems. Whether the project is new construction or upgrading (retrofitting) an existing system, several fundamental issues must be addressed prior to the installation process. Answers to the following questions will provide valuable information:

Will other systems (e.g., access control) be integrated with the CCTV System?

What transmission mediums will be used?

What is the project budget? Has it been planned, committed and

Approved?

What are future system requirements regarding upgrades?

Will application requirements change in the future?

Each of these questions helps the designer to define a system that meets the customer’s needs for the present and the future.

Will the CCTV system be integrated with other systems? Will the CCTV system need to supply information regarding access control or other systems? What level of integration is required? If there is an existing CCTV system, are there component compatibility issues that must be addressed? What is the most efficient and cost-effective transmission medium for the system? If an existing CCTV system is being upgraded or supplemented, what is the existing transmission medium, and should the upgrade include changes to the existing transmission medium? What is the project budget? In a sense, the answer to this question can define many of the design elements for a CCTV project. There are obviously many ways to proceed while satisfying any budgetary restrictions. The basic options are to reduce the number of components (and therefore coverage) or use components with fewer capabilities or lower quality, e.g., monochrome cameras instead of color, or a camera with generally lower specs (resolution, sensitivity, S/N) as long as the component will still provide the performance required for the application. Also, how was the budget determined? Is it based on sound preliminary research or a "guesstimate?" Have the decision makers committed to it and has it been approved? Does the option exist to review the budget or is the designer locked into the approved amount?

Designing a New System

What are the requirements for future upgrades? As newer technologies become available, is the customer's expectation that these will be incorporated into the system design. Is there a planned migration path to accomplish this?

Related to this last question is another: will application requirements be changed in the future? Will enhanced functionality be required at a later date? That is, will the function of the CCTV surveillance system or the overall security system change in the future?

For example, is the company planning to expand its facilities locally or even remotely? Consider a commercial laboratory that is planning to move into new markets within the next five years. The new business will demand new levels of access control and CCTV coverage. Being aware of that future requirement can impact decisions regarding the current decision. Answers to all of the above questions sets a baseline for CCTV system design. These are primary issues. Secondary issues are the "nuts and bolts" aspects of system design, and careful attention to these primary questions will automatically define many of the hardware issues.

A carefully designed CCTV surveillance system will ensure:

1. adequate coverage
2. Extendability for future additions and enhancements.
3. Satisfied customers.

Installation Tools & Techniques

All cameras need to be powered and have a way to get the video signal back to the monitor and recorder. The most reliable way to achieve this is to "hardwire" your camera system. Some camera locations may require wireless transmission of the video signal but you should avoid using wireless if possible. Wireless is best suited for temporary surveillance applications.

Video/power cable can be purchase pre-made in specific lengths like 25m, 50m etc. It can also be purchased in bulk rolls of 500m or 1000m that can be made to custom lengths.

Although using pre made cables is perfectly acceptable there are drawbacks over making your own. With pre made cables, the connectors are already on the wire so you have to drill a larger hole to pull the wire through an opening.

You may also have excess wire to deal with. This is especially bad when it's on the monitor end. Making custom cables makes for a neater installation and costs less per foot/ meter.

If you decide to make your own cables you will need some specialized tools. One is a wire stripper, the other is a crimper. You will use these to prepare your cable for "BNC" connectors. Using these industry standard connectors will insure that your wiring is compatible with most cameras on the market. It also allows you to replace or upgrade your cameras at a later date with out having to rewire your system.

Most installations require that you hide your wiring as much as possible. You can do so by "fishing" the wire through your walls & ceilings. We first drill a 3/4 inch hole in the top wall plate as well as where you will be mounting the camera.

This size hole will allow you to use the pre-made cables or the custom made cables. We insert small flexible fiberglass rods into one hole and try to push it out the other end.

They come in 6' lengths and can be combined with other rods. This is especially helpful when pulling wire over long distances like a drop ceiling.

Once the rod is sticking out the other end, attach your video cable to it and pull the wire out until about 18" is sticking out. You'll have plenty of wire to work with.

Another type of wall fishing tool is called a fish tape. It is a long metal wire that is wrapping onto a spool. You simply pull out a small amount and feed it into your hole. Keep pulling and feeding it until you can attach your video cable to it.

Individual transformers or a power distribution panel can power you camera system. For neater installations especially for systems with more than 4 cameras use a power distribution panel. A power strip with 8 outlets fills up rather quickly when you also plug in the monitor, recorder and 4 transformers.