Wireless has become so common today, that it is taken for granted. Cellular phone technology has almost replaced the traditional landline for many families. Cell phones are so prevalent and widely used that the movie theaters must remind patrons to turn them off, so that they do not disturb others in the theater. Wireless Internet is available at most hotels and coffee shops, the airport and even some trains. Cities have jumped on the bandwagon by providing wireless Internet service for homes, businesses and apartments within the city.
The popularity of wireless has far exceeded the expectations of its capabilities in just the last 10 years. Wireless products have become available for many applications that, not long ago, were hardwired only. It is becoming an integral part of our everyday lives.
The security market has used wireless keypads, sensors, radios and video transmitters/receivers for years. In short, wireless applications have exploded, while the cost has imploded. Today, any time there is an application that requires flexibility of movement, wireless is the first and often the only approach considered. Future applications of wireless are limited only by our imagination.
Wireless in Security Applications
Wireless applications are everywhere, they are relatively inexpensive, they allow tremendous flexibility and they almost always provide the desired results. Why then is anything hard-wired?
There are some issues with wireless that must be understood and incorporated into any electronic application, especially when used in security. The basic issues of wireless technology applications:
* Power is necessary for wireless to operate; and
* Reception can be a problem with wireless.
Power and Reception Issues
When designing or installing wireless security applications, it is important to remember that the wireless product requires electrical power. The power can be the standard 120 Volt (V) Alternating Current (AC) available in the electrical wall outlet, a battery, a solar panel, a low-voltage transformer or power supply. Most security applications will require low-voltage, solar or standard 120VAC power. Since wireless transmitters require power, the wireless applications are not totally without wires.
Another issue is reception. Recently, I purchased a wireless device that transmits a radio signal via Frequency Modulation (FM) to a car radio. The wireless device allows me to listen to songs on my vehicle's radio when reception would be impossible from a radio station while I am on long trips in sparsely populated parts of the country.
The reason that FM signaling was developed was to address and correct the signal loss and fade issues associated with AM radio signals. We have become accustomed to signal loss when using cell phones, in fact, there are commercials that advertise a person checking reception by saying “Can you hear me now?”
Loss of reception can occur for several reasons. For electronic security applications, the typical issues are: weather; signal blockage/loss; interference; and power level.
The weather impacts wireless in several ways. The level of humidity can negatively impact signals. Most people have noticed what is called “rain fade” on their television when using a satellite TV antenna. The picture quality degrades, becoming more and more grainy, until the signal is totally lost. Weather – or more accurately, seasonal – changes, can impair wireless signals through the growth of vegetation, which can block or shield RF signals, especially “line-of-sight” signals, such as microwave transmissions.
A tree in the path of a high frequency wireless signal may not cause a problem in the winter, when the tree is bare of leaves, but when summer comes and the tree is full, the signal can be blocked. The negative impact of vegetation on a signal will increase as the frequency of that signal goes higher.