For the Home Technology Enthusiast

Home Security Basics



Home Security

Home security comprises video surveillance, intrusion detection and alarming. A variety of technology and systems are available in the market place for implementing home security. We review below the more commonly used ones.


Video surveillance

Video surveillance is a key part of home security systems. Both indoor and outdoor video surveillance systems are used for this purpose. Most commercial low-cost systems are essentially what in the industry is known as closed circuit television systems. By closed circuit, it is meant that the video signals are confined and used in a private environment as opposed to being broadcast over the air or cable to the public at large.


Most surveillance CCTV systems use simple analog cameras to capture the video and transmit these signals to a central viewing station for display on a monitor. This transmission can be over a cable or can use wireless RF over public radio bands. Such RF signals of course are not secure from tapping and therefore the choice to use RF transmission must be made with caution.


Such closed circuit TV systems are reasonably effective, especially when backed up by a recording mechanism that records video on a continuous basis. Such recorded video can be used as evidence of intrusion. 

Some disadvantages of the simple CCTV based surveillance system are:

  • Human presence is needed to view and detect intrusion in real-time

  • Cannot be easily accessed and controlled through a computer

  • The signals - when wireless devices are used to capture and transmit video - are susceptible to interference and therefore cannot assure good quality at all times

  • Recording systems (typically VCRs or like systems) have to be maintained manually such as swapping tapes, restarting the recording process, etc.

Digital video technology and its suitability for integration into the computer network is fast becoming a preferred alternative to the analog CCTV systems described above. A digital CCTV surveillance system overcomes all the shortcomings of the analog CCTV system. Its greatest benefit comes from its seamless integration into a computer network. Better still, once integrated into the computer network, it becomes an entity that can be monitored and controlled over the Internet. This opens up infinite possibilities.


Digital video allows for things such as subject identification (using pattern recognition technology), conditional alarming based on scene change, extracting frames of video as still shots for easy email, and a myriad of other features that are of true value to users. Recording digital video can be done on a computer hard disk. Such recorded video can be transferred over the Internet to another one instantaneously for backup as an example. The list of the benefits of going digital is huge and is limited only by our imagination.


In the home security context, digital video based surveillance systems are becoming more affordable by the day and will in all probability reach a parity point with analog systems. Another important aspect of a digital video surveillance system is its compatibility with an IP-based home network. 


Two alternatives are available to users for implementing a digital video surveillance system - one using a camera server and analog cameras and the other using only digital cameras.


The first method involves the use of a camera server. The server's job is to interface to the simple analog cameras used in the analog CCTV systems and convert their analog video to digital form and present them in a form suitable for transmission over home networks. Additionally, the server supports a browser interface for configuration, control and viewing of the video.


The second method uses digital cameras that connect to the home network directly. Such cameras have built-in browser interface support for configuration, control and viewing of the video.


The choice of whether to implement a system using the camera server approach or using the digital camera approach doesn't have to be a hard either/or. Depending on your situation, a combination may be the optimum solution. As a rule of thumb, if you have more than four cameras, then a server based implementation may be more cost-effective. Even so, it may be worthwhile to add a stand-alone digital camera to that network as a fifth camera especially if the server is capable of interfacing only up to four analog cameras.


Intrusions Detection and Alarming

Intrusion detection is often a combination of motion sensors and door/window open/breakage sensors. Upon detection of intrusion, they send either X-10 (or other) compatible signals to controllers or simply activate a dry contact which is in then sensed by controllers. The connection between the sensors and the controllers are either over wires or over RF signal.


Alarming upon intrusion detection can be implemented as simple local audio-visual systems such as sirens and flashing lights or as auto- dialing and paging systems that send out messages to corresponding receivers.


Given the variety of surveillance, intrusion detection and alarming systems available in the market, a home user would be best served with a customized solution that above all meets the desired level of security at the desired overall cost.