Since the first bombing of the World Trade Center where terrorists tried to bring down the structure by placing explosives in a vehicle in the underground parking, security directors have been paying closer attention to these facilities. Some would use manpower to secure the area. Most would use a combination of technology and manpower. Today, with the advancement in CCTV, analytics and access reader technology, security directors are looking more at technology to secure their parking facilities and interfacing it with their security management system.
Access control readers utilize three levels of frequency: low frequency (125 kHz), high frequency (13.56 MHz) and ultra high frequency (902 to 928 MHz). Each frequency has its advantages. This depends on entrance style, read range, speed of entry, model of vehicles, interfacing with existing security management systems and budget.
Low frequency readers have a maximum read range of 24 inches. This depends on the antenna size in the reader and credential used. At the door entry points, readers with ranges up to eight inches may suffice. This is also the case when interfacing with an intercom system at the gate entry. Because the driver must present the card to the reader, a read range of 24 inches would be needed.
The read range also depends on the credential used. The primary credentials used in low frequency readers are passive. The credentials have no battery and are energized by the reader’s RF field. When using a card-type credential, you should get maximum reading distance. If you decide to use a key tag credential to fit on your key chain, expect the read to be reduced by about one-fourth of its range.
High frequency readers have a maximum read range of three inches. These types of readers are starting to find their way into parking facilities where the local transit card acts as a debit card and also an access control card.
Ultra high frequency readers have become the reader of choice for parking facilities due to their read range. There are two types of ultra high frequency credentials: passive and active. Passive tags are inactive until they are enabled by the reader’s field to send out the embedded information. The read range of passive tags is usually up to 20 feet. Active tags are assisted by power from their batteries. They are primarily used for toll collection but are also used in parking facilities where the read range and RF blocking are a concern. The batteries have a limited life. You will need to consult with the manufacturer for life expectancy on the batteries. The read range will exceed 35 feet.
When trying to determine if an active or passive UHF tag would best fit your installation, the following criteria need to be considered: environment; vehicle type; and entrance design.
Interfacing with security
A major development this past year has been the interfacing of parking facilities with the existing security management system. This is simplified by standardizing with Wiegand encoding in credentials for both people and vehicles and Wiegand interface between readers and system panels. Most manufacturers offer a second layer of protection by offering an encrypted credential.
The 26-bit Wiegand format assigns a facility or site code (8 bits) and an ID number or personal identification number (16 bits), and two parity bits for error checking. The 26-bit code has now been expanded to 64 bits or more.
The personal identification number associates that credential with an individual or vehicle. The facility code limits the accessibility to that specific facility. In today’s security management systems, the parity bits add to the accuracy of transmitted data.