1. Plenum-rated wire must always be used for all access control devices.
   a. True
   b. False
   
   
2. Which type of wire should be used for a request-to-exit (REX) motion detector?
   a. 16/2
   b. 22/4
   c. 22/6 shielded
   d. Cat 5e
   
   
3. Which type of wire should be used for a magnetic lock?
   a. 16/2
   b. 22/4
   c. 22/6 shielded
   d. Cat 5e
   
   
4. Which type of wire should be used for a standard Wiegand card reader?
   a. 16/2
   b. 22/4
   c. 22/6 shielded
   d. Cat 5e
   
   
5. Data communication cables run between access controllers always should be shielded.
   a. True
   b. False
   
   
6. Which of the following factors affect the type of cable used for an electric lock?
   a. Wire length
   b. Current draw
   c. Voltage
   d. All of the above
   e. None of the above
   
   
7. Metal oxide varistors (MOVs) are used to convert AC to DC.
   a. True
   b. False
   
   
8. The higher the AWG the larger the wire gauge.
   a. True
   b. False
   
   
9. Which of the following can be used to calculate voltage drops?
   a. Kirchhoff’s Law
   b. Ohm’s Law
   c. Thevinin’s Equivalent
   d. All of the above
   e. None of the above
   
   
10. Fail-safe locks require power to unlock.
    a. True
    b. False
    
    
11. When designing an access control system, what codes/standards should be considered?
    a. Local building/fire code
    b. Electric code
    c. ADA
    d. All of the above
    e. None of the above
    
    
12. Surge current is the amount of current an electric lock draws while energized.
    a. True
    b. False
    
    
13. Grommets or insulated bushings should be used when running cables through steel studs.
    a. True
    b. False
    
    
14. Doors with easy egress hardware require a REX device to allow people to exit.
    a. True
    b. False
    
    
15. In order to utilize anti-passback, which of the following is required?
    a. Request-to-exit motion
    b. In-and-out readers
    c. Request-to-exit button
    d. All of the above
    e. None of the above

What’s Wrong with This?

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Wally `Larman was asked by one of his commercial accounts to add access control to a server room door approximately 200 feet from the access control panel. He carefully selected devices that were compatible with the existing system, including a 24 V 750mA electric strike, satisfied all codes and requirements, and installed them as shown in this diagram. When he was finished, he tested the system and all appeared to be in proper working order, but his customer later called and said that periodically the server room door would not lock. Wally replaced the electric lock, but the problem continued. Can you see what Wally did wrong and what he must do to correct the problem?

5-Minute Tech Quiz Answers

1. b - Plenum-rated cable should be used whenever wire is run above a drop ceiling when the area above the ceiling is used as an air return for the HVAC system. If there is no drop ceiling or if there is a ducted air return, plenum-rated wire is generally not required.
   
   
2. b — Although Cat 5e cable could be used, it is more expensive than standard 22/4 cable.
   
   
3. a
   
   
4. c
   
   
5. b — Many inter-panel communication cables do not require shielded cable.
   
   
6. d
   
   
7. b
   
   
8. b
   
   
9. b
   
   
10. b — Fail-safe locks require power to lock. Fail-secure locks require power to unlock.
    
    
11. d
    
    
12. b — Surge current is the amount of current a lock draws when it is initially energized. It typically is higher than the normal current draw of the lock.
    
    
13. a
    
    
14. b — Although easy egress hardware allows people to exit without using a REX device, it is common to install a REX motion so that door status can be supervised. Typically, the REX motion is programmed to shunt the status switch but not release the lock.
    
    
15. b — Because anti-passback requires users to swipe before they can exit or before they can enter, using a request-to-exit device defeats the purpose, although one may be used to allow a receptionist to grant a visitor entry or exit.

Answer to: What's Wrong with This?

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Wally’s problem is caused by the size of wire he ran for the electric lock. Using 22 AWG cable for a 200-foot run will cause a voltage drop of approximately 4 volts, which is causing the fail-safe lock to release or decreasing its ability to secure the door. Wally should replace the lock cable with a larger wire, minimum of 18 AWG, reducing the voltage drop to about 2 volts. When designing the cable runs, take into account the length of the run and the current draw of the lock, because these factors will affect how much voltage is lost in the cable (voltage drop). To calculate the voltage drop, you can use Ohm’s Law: voltage = current times resistance.