Digital Electronics Computers & Video Security

A forum for recording my findings and discussion of matters related to electronics, computers, security and other technical subjects.

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Location: Queensland, Australia

Automation and Integration Architect

Sunday, September 24, 2006

Premises security (part 3) Wired or Wireless ?

Last installment we looked at a couple of different cameras which can be installed to give fairly good picture quality.

One thing I forgot to mention was that the light-handling ability of some of the cheaper cameras is VERY poor.
I have returned several indoor cameras because they simply wash-out the scene when it becomes brightly lit - such as in full sunshine.
The moral here is to check before destroying the packaging !

Today I want to look at the first of the topics you should consider if you've decided to give Do-It-Yourself surveillance a go.
This topic is Should I Use Wireless or Wired security?

First of all, it needs to be said that no matter what type of system you install, they are all susceptible to intentional disruption.

There are a number of wireless based home security systems on the market.
Most reputable wireless units have jamming detection built into them, which will dial a monitoring service if radio-based interference is detected.
One I have personally found to be quite adequate for my purposes on small security installations, is the LYNX security system from ADEMCO.

Differences between the two types
The major differences between a wired and a wireless installation are that the sensors all need regular battery maintenance and that intrusion can be effected without having to actually enter the premises.

Obviously wireless installations lend themselves to difficult sites and also for speed and ease of installation. On the other hand the cost of the sensors is greater as too are battery maintenance costs.

Wired installations are conversely more difficult to interfere with because physical access is necessary. They also support cheaper sensors, although this can easily be offset by the cabling costs.
Wired installations also have the benefit of a central power source rather than having to maintain relatively expensive long-life batteries (often Nickel Metal Hydride) in a dozen different and often difficult-to-access places.

Special considerations for video installations
Where video surveillance is concerned, there are some additional issues which need to be considered.
The cameras still need a power source so they are NOT truly wire-less!

Because the publicly available wireless cameras operate on a public radio channel shared by many other devices and users, general non-malicious interference can cause such severe signal degradation as to render the image(s) useless. Also, because the signal is usually NOT encrypted, anyone within 100m can view what is being "seen" by the cameras.

Take care what the camera "sees"
This latter point may not be so bad in outside settings where no pattern of traffic is obvious nor anything of value visible. Within a building however, to monitor your heirlooms cabinet or your $10,000 home theatre equipment is rather like putting signs out within 100m of your premises to advertise what you have that's worth stealing!
Another thing that is forgotten when using wireless monitoring, is that your patterns of movement can be very accurately recorded so thieves know when you are likely to not be in a room or building.

Image Quality and Distance to Cameras
Picture quality and reliability is significantly superior with a cabled video system but does have distance limitations without signal repeaters.
Image quality is often more "noisy" with radio and also has distance limitations which are harder to overcome than with cable extenders.
My own experience with wireless cameras has shown that while 100m is possible with clear line-of-sight between the camera and the receiver, ANY obstacle will drastically degrade the distance/quality of transmission

Next installment I'll start talking about monitoring the devices and how they may connect.

If there is anything you disagree with me on, or want clarification about, please feel free to add comments

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