An Earnest Proposal for Solving the Problem of False Alarms - Part 2

April 4, 2005
Bill Warnock takes an in-depth look at the physical and electromagnetic factors that affect false alarms

False alarms don't magically happen, and security equipment relies on the integrity of a home and the integrity of electronic systems. Come, let us step back and take a good hard look at what factors we're dealing with.

One of the first set of questions you have to ask is this: Was there proper site preparation to be assured the proper sensors were selected for their intended environments? Was it a proper site preparation? Yes, you must know the environment inside and out like the back of your hand. Let us start with the environment outside the protected structure. That's U.S. Army talk for building.

You're probably asking why we would examine the area outside a structure in terms of its effect on false alarms, right? Here's why: The noise, vibration and electronic interference will determine for the most part what type sensor is placed and where, the type of conductors used and method and location of control panel installation.

Further, it gives the owner, planner and local law enforcement some idea of mitigation necessary for a successful installation and operation. This may not be a one-time fix, as the environment changes so must the mitigation and perhaps sensors or the entire system either upgraded or replaced. Let's begin:

  • Is there a fence surrounding the property? What is it made of? How far away from the building is it? If it is chain-link fencing, has it been properly bonded and grounded?
  • What are the extreme wind velocities?
  • How often does the area have lightning? Which are the worst months and frequency based on information from isokeraunic maps?
  • Are there any high-tension lines close to or above the property where the building is located?
  • Are there electrical transformers near the property line?
  • Are there any sewer lifts, pump houses, welding shops, quarries with excavating machinery, air conditioning equipment, water pumps, agricultural equipment on or near the building?
  • Are there any roads close to the building? What are the peak hours of traffic?
  • Are there any major roads or interstate highways close to the perimeter boundary? Are they within 2,000 yards or 1,828.8 meters? What are the peak hours of traffic?
  • Are there any railroad tracks close to the perimeter boundary? Are they within 2,000 yards or 1,828.8 meters? How often are they used?
  • Is there an airport, private or commercial, domestic or international, close to the perimeter boundary? Does the landing/takeoff pattern or flight path go over or come close to the perimeter or building? What are the minimum altitudes?
  • Are there ground or weather radar sites close to the perimeter boundary? What kind of radar is used and what are the expected radiated energy levels?
  • Are transmission towers for television, AM-FM radio, to include amateur radio stations, or microwave close to the perimeter boundary? What are there operating frequencies and radiated power?
  • Are there maritime installations close to the perimeter boundary? Are they within 2,000 yards or 1,828.8 meters? What is the activity and do they include harbors, canals or channels?
  • Are there any rivers or lakes adjacent to the perimeter boundary? Are they navigable? Are they within 2,000 yards or 1,828.8 meters? Is the traffic light or heavy on a daily, weekly, seasonal or year-round basis?

To assure trustworthy sensor selection and installation, all these variables must be known and taken into consideration. Additional shielding such as special conductors (cable), ferrite beads or RFI gaskets may be required.

The Building

Now we tackle the building itself, both exterior and interior. You'll need to ask these questions:

  • Is the building one story, two story or multiple stories?
  • Does the building have an attic, crawl space, storage area, and maintenance area, garage parking, basement and/or sub-basement?
  • What is the exterior composed of: wood, brick, poured concrete, cinder block, aluminum, steel or wood siding or combinations thereof? If it is concrete, is the ferrite content known?
  • What are the thickness of the exterior walls to include make and type of insulation?
  • What are the dimensions of the building, length, width and height?
  • Are there any exterior wall vent openings, number, location and type? Are there any bars, grills, and expanded metal mesh or like material covering the opening?
  • How many exterior doors are there? Where are they located, what type are they (wood, solid or hollow core, metal or metal clad or glass) and how are they installed?

Now as we get into more intricate construction, let's examine some construction terminology before we move forward.


  • Simple butt cannot be taken apart. Use RH or LH doors.
  • Loose-pin permits removal of door without unscrewing hinges.
  • Loose-joint permits removal of door without disturbing hinges or pin.
  • Rising butt is used when heavy carpeting interferes with opening of door. As door is swung open, the door rises slightly to clear the carpeting.
  • Ball bearings are permanently lubricated. They are recommended for heavy doors opening outward.

Door and Opening Parts

Here's the terminology: Top rail, stile extension, panel lock rail, hinge stile, latch stile, stile extension and bottom rail. Don't forget casing, head jamb, stop, jamb, saddle or threshold. And the he mullion is the middle casing for double doors.

A word of explanation is needed here. Construction standards leave a lot to be desired. To avoid complications and facilitate volume buying of door and frame combinations, the buck, or hole cut for a door, are often oversized, usually by one or two inches.

When the frame and door are installed, the space between the edge of the buck and the frame are filled with wooden wedges at two or three points, then plastered or trimmed over. In a relatively short period of time the wedges loosen after repeated opening and closing of the door, and the frame begins to float in the resulting air space or void.

To facilitate illegal entry, a modified car jack or fireman's frame spreader is placed just above the doorknob and or keyway. The spreader evenly applies pressure to both latch and hinge frames. The door yawns open. If rubber cups or padding are used, no marks will be left. Since wood and metal have memory, the frame quickly returns to its original position and form when briefly prized apart. When law enforcement responds to an alarm, they find all doors closed and locked and they report the dispatch as a false alarm.

When the owner returns and finds missing property and calls law enforcement, the report of a false alarm may put his insurance claim in jeopardy.

Here are some questions you have to ask about each door:

  • What is the direction of swing: right or left?
  • Brand name and type of locking device(s), rim, mortise, cylindrical, dead bolt? Vertical or horizontal? At least 2 inches long and single or double cylinder?
  • If there is more than one locking device on the door? If so, which one is used as the primary lock?
  • Did the builder, former owner or current owner install the locking device? If installed by the builder, how many dwellings did that builder in that locale construct?
  • Is there any locking hardware within 40 inches of any glass panel?
  • What type of hinges are used: simple butt or loose-pin? If loose-pin, are pins exposed? What are the lengths and type of screws securing hinges in frame and door?
  • In regards to the doorway, what are physical conditions of exterior and interior casings, head jamb, side jambs, and threshold? Is the side jamb framing made of metal or wooden 4x4s, double or single 2x4s? Are filler studs used? How are they held in place? Is there a double header securing the head jamb? Can side jambs be spread apart to compromise the locking device?
  • Consider the faceplate. What is the physical condition of recess, if any? What are the lengths of screws securing faceplate?
  • Strike plate recess or box? What is the depth and condition of recess and length of screws securing strike plate?
  • Is there a viewer installed in the door? What is its field of view? Is the viewer equipped with an interior swinging cover?
  • Are supplementary security devices used, if so what are they?

What is condition of the doorway, exterior and interior casings, head jamb, side jambs, threshold and rails? Is side jamb framing made of metal or wooden 4 x 4s, double or single 2 x 4s? Are filler studs used? Can side jambs be spread apart to compromise the locking device? Can sliding door be raised from either top track or bottom rail? Have large headed screws been inserted into the head jamb and framing at both ends and in middle?


Describe condition of the exterior and interior casings, head jamb, side jambs and threshold. Is side jamb framing made of metal or wooden 4x4s, double or single 2x4s? Are filler studs used? If so, how are they held in place? Is there a double header securing the head jamb? Can the side jambs be spread apart or removed to expose track and guide rollers to manipulation or removal?

What is the construction of the door leading into the facility, locking devices, type and condition of hinges, and condition of doorway?


How many exterior windows are there in the building? Where are they located?

What type of closing or locking hardware is used on each window? Do they offer light, ventilation, and visibility but NOT easy access? Are they: sliding, push out slide-up casement, single or double hung, wood or aluminum, transparent or translucent, thermal, clear or tinted, solid or decorative?

It should be remembered the function of a crescent latch on a double hung window is to keep the upper and lower windows together.

Are any windows equipped with key operated locking devices? If so, what are the types and brand names?

If a locking device is used, the key to window lock should not be placed closer than 40 inches from any glass panel.

Have double hung windows been pinned? If so, what method of pinning was used? At each top corner of the inside sash, a 7/16-inch hole should have been drilled through the inside sash and three quarters of the way through the outside sash at a slight downward angle. Two 5/16-inch diameter dowel pins, one on each side of the window should have been inserted. The pins should fit loosely enough in their holes so that they are easy to insert and remove.

Are the windows ever opened for ventilation? When?

What method is used to preclude unauthorized entrance? Are windows equipped with security stops? If not, a separate set of holes can be drilled into the outside sash approximately three to four inches above the inside sash so that the window can be left open for ventilation. This prevents the window from being opened further than the three or four inches allowed.

Are interior window panels covered with any vandal resistant film? If film is used, is it UL 972 listed? What kind of film was used what NIST approved laboratory performed the tests for that type of film?

Did the manufacturer's approved contractor install it?

Electrical Systems

  • Now we turn our attention to the building's electrical system.
  • Does the electrical system exhibit any of the following symptoms?
  • Do fuses or circuit breakers blow or trip often? Which circuits are most affected?
  • Are there lights that flicker when heating or air conditioning equipment or appliances are turned on? Which lights are more affected than others? Do some lights burn out more frequently than other lights? Which circuits?
  • Is AC ripple (vibration to the touch) present on equipment chassis? Is AC rippling constant or intermittent? Is it seasonal? At what times was AC ripple the strongest or most noticeable? In addition to interference, shock or electrocution is possible under the right circumstances.
  • Do all appliances operate at full power? Which appliances are more affected than others?
  • Does the television or computer screen image shrink when a heavy appliance is operating?
  • Is there interference to television or computer screen images when a microwave oven is in use? With commercial television, is there interference noted? What channels other than two through four are affected? What electrical circuits cause this interference?
  • Is the exact location of each wire run known? Is this borne out by architect or contractor "as built" drawings? Have modifications to the electrical system been recorded or added to existing drawings? This will be critically important when the alarm installation is contemplated.
  • The drawings and the narrative prepared for a project must contain information how much separation that will be maintained between cabling carrying high voltage alternating current (AC), low voltage AC and low voltage direct current (DC).
  • There should be at least 12 inches of horizontal and 6 inches of vertical separation between conduits and/or conductors carrying AC from those carrying DC.
  • What are the grades and condition of each electrical switch and receptacle used in the building?
  • If the switch is turned on and it is moved from side to side, does the light flicker?
  • Are receptacle slots and switch fronts routinely vacuumed of dust or other debris? Do plugs stay in the receptacle without the prongs being pinched or spread apart?
  • Is the tension good on each receptacle? Does it meet a 10-ounce pull test?
  • Is there any kind of buzzing or hissing coming from any of these devices? Is any device hot to the touch?
  • How is each electrical switch and receptacle wired? Is wire attached to binding post screws, quick-wire push-in terminals, or rear wiring ports with binding post compression?
  • Is correct polarity maintained - black wire on brass colored screw, white wire on chrome colored screw, red wire on brass or chrome colored screw, green or bare copper wire on green colored screw?
  • If a white wire is a current carrier, is it marked with black paint or tape at every point where the wire can be accessed?

Telephone System

Now we must look at the telephone system. What is the quality of service you receive?

Is there noise on the line? Can you describe it? There is noise within normal hearing range and there is noise below and beyond normal hearing ranges.

Does your telephone ring during a thunderstorm?

When talking to someone can you hear others, not a party to your conversation, talking? Is that speech clear or garbled?

Most telephone service has been vastly improved in recent years to support computerized traffic and the like. There may be, from time-to-time, types of interference that could play havoc on an alarm system especially one not containing discriminatory circuits designed to filter out all signals not being sent from the monitor panel to the central station and back. Bottom line, electricity is still the mode.

In my neighborhood we have fiber optic lines. Fiber optic cable is a communications messenger. It faithfully carries as light energy, all the converted electromagnetic intelligence data, to include noise, from a transmitter to a receiver where it is converted back into electromagnetic intelligence data again. It should be remembered noise is also intelligence -- unwanted intelligence. Electricity and grounding get two strikes at the system at two different locations: on the transmitted side and on the received side.

This may be a lot of questions, and perhaps a more exhaustive site survey than you had planned on, but remember that all these factors can affect an electronic security system.

[Editor's note: In the next part of this series, Bill Warnock takes a look at what these factors mean in terms of false alarms.]

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