Q
How does the Homeland Security threat level impact an access control system?
A
Some companies may have internal policies to change how access is granted to areas based upon which of the five threat levels are in effect for that facility. Specific plans will vary, but for example, a facility might leave perimeter doors unlocked during business hours in Low Condition (Green), lock them, but require only a card in Guarded Condition (Blue) and require a card and a code or limit access to some areas in Elevated Condition (Yellow) or above. Because a change in the threat level could occur suddenly, you should plan for it. Individually reprogramming each user is not an option, so you should find a combination of features that allow you to accommodate this need. Some systems support system wide changes based on the threat level.
Common Sources of Interference
Q
What are common sources of interference that might impact data sent in a system? What steps should be taken to avoid this interference?
A
Likely sources of electromechanical interference (EMI) or broadband noise include: motors, pumps, generators, DC-AC or DC-AC converters, non-interruptible power supplies, AC switching relays, light dimmers, CRT’s, induction heaters, computer monitors, televisions, AC power cables, lock power wiring, phone and other signal wiring. You should also read the installation and operation manual to check for other sources of interference that might impact your specific equipment.
It is a good idea to inspect the site before starting the installation of any equipment to avoid any possible sources of interference. Do not put the reader wiring or data wiring connecting controllers together in one conduit with the AC power cables, lock power and other signal wiring. Adequate separation of at least 12 inches should be kept between reader or data wiring from all other wiring and sources of interference. Wiring should not be installed near elevator controls or electrical switching equipment. Shielded cable and dedicated power supplies can also limit interference. You should also avoid using a single power supply for the reader and the magnetic lock because surges from the lock will probably impact the reader.
Proximity Reader Range Fluctuation
Q
What can make the range of a proximity reader to be lower than specified?
A
While some readers may be designed for mounting on metals, the read range will drop severely for many if the reader is mounted on or near metal such as an aluminum or steel doorframe or in a metal box. Separation of at least two inches or insulation from the metal can reduce the impact. Lower than specified voltage can also lower the read range. Use of an inadequate power supply, improper sharing of power supplies or high resistance because of use of the smaller than required wire size are common causes of lower voltage.
Brad Shipp is a former Executive Director and Training Director for the NBFAA where he authored several NTS courses, including the Access Control Certification course. His involvement in the access control industry dates back to 1974 and, in 1986, he became an instructor for the NBFAA National Training School. Shipp has served on several law enforcement, regulatory and industry association boards and has been honored for his service by the False Alarm Reduction Association and the International Association of Security and Investigative Regulators. Send in your access control questions to [email protected].
"Some companies may have internal policies to change how access is granted to areas based upon which of the five threat levels are in effect for that facility."
