[IMAGE]12267[/IMAGE]How to Extend Existing Systems
Wireless access and intrusion systems typically operate up to 200 feet between the door and the panel interface module (PIM) for indoor applications. A key factor here is line of sight between the wireless component and the PIM is not necessary. Signals are able to penetrate cinder block, plasterboard and brick walls, as well as many other nonmetallic materials for simplified system design and implementation.
For outdoor and remote applications, wireless eliminates costly trenching and/or pulling wire to unrealistic lengths. Consider these benefits in a scenario such as installing an intrusion alarm on the equipment shed at an athletic field or having cameras watch over perimeters at the furthest extremes of the property.
“We’re doing some pretty unique things with wireless here,” Vanderpoel says. “They include spanning an entire athletic field to using one PIM to get a signal to three different buildings.”
End users and installing security contractors alike are finding wireless systems are ideal for garages, parking lots, airports, utility companies and military bases. Even more impressive, optional directional or gain antennas are available for still longer distances.
Wireless also offers additional functional advantages. The most obvious example in an intrusion system is a wireless security pendant that gives select employees the ability to trigger an alarm from anywhere in the building or parking lot. Pendants also can be used as safety buttons for employees who work alone in the event of an accident or emergency.
WiFi, 900MHz to Consider
Depending on the project, the term wireless can entail different types of communications. For access control and intrusion systems, there are two major types of wireless. The first is where one installs 900MHz communication to a PIM and onto a hardwired source network. The second is 2.4GHz/802.11 WiFi, in which communication goes from the lock or sensor to a WiFi antenna and onto a network.
Signal propagation and strength through building walls is stronger for 900MHz signals versus the shorter wavelengths of 2.4GHz signals. Typically, if a 2.4GHz system is installed in a building, additional WiFi antennas will likely be needed to support an equal number of wireless locks or sensors over a given floor plan.
In WiFi systems, this can mean additional installation costs by assuring antennas have closer proximity to the locks to ensure reliable operation. In addition, independent WiFi locks require unique IP addresses. Thus, there is greater involvement with the IT department and, all too often, extra internal fees are charged for each IP address. With 900MHz solutions, a single IP address manages 16 or more doors.
Let’s take a closer look at some of the pros and cons of these two major types of wireless. The 900MHz solutions provide greater range, or distance, between the network antenna and the lock/sensor. They also offer more secure communication between the lock/sensor and the network, which is why they are typically preferred for access control and intrusion systems.
Conversely, 900MHz systems are limited to the Americas and Australia and provide lower data rates. Of course, the data rate for access control or intrusion is minimal when compared to the Internet usage on a 2.4GHz wireless network.
WiFi is a global solution with higher data rates. However, it has less range than a 900MHz solution and obstacles can dissipate waves. Also, WiFi is becoming increasingly crowded, which can negatively impact system reliability.
WiFi communication is designed for the transmission of large data files, such as E-mail and video on PCs. It uses more power than 900MHz. In WiFi video applications, batteries are typically not used. However, batteries are often used with access control and intrusion systems, whose control data is small but nonetheless requires significant power to communicate.
The 900MHz solution provides up to two years of battery life (with four AA batteries and a 10-minute heartbeat). Additionally, a new Schlage-patent-pending “wake up on radio” feature extends life by working in parallel with the 10-minute heartbeat. Without waking up the entire lock, it listens for complementary commands every 10 seconds and responds upon detecting a command. To achieve such real-time availability with WiFi, the installer needs to hardwire the power, which then eliminates the value proposition of a wireless platform.
With the 900MHz solution, the entire access control system detects when someone is at the door. The lock captures information such as request to exit, door position and card data and sends it to the host immediately in real-time. The access control management system makes a decision to unlock the door or not. Since WiFi cannot afford to use all that power, decisions are made solely at the door. Any updates, such as the change or termination of a person’s access rights, may not have yet reached that door before, say, the ex-employee does.
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