Published on September 2nd, 2008 | by securityguy0
Bypass contact switch alarms
Contact switches are the most frequently used pieces of alarm detection equipment and, interestingly, are the easiest to circumvent. They are typically applied to moveable doors and windows in both homes and businesses. They come in many shapes and sizes and are available in various colors, though the most common are gray and brown.
The contact switch consists of a switch and a magnet. You guessed it – when properly aligned, the magnet holds the switch closed. In Figure 2, the switch is being held together by the magnet that is placed directly below it. In Figure 3, the switch is open position because the magnet is no longer there to hold it together.
The most popular type of contact switch can be seen in almost any business that has an alarm system. They are almost always found on the doors of the establishment to detect any illegal entry during closed hours. These are called surface mount switches because they are mounted on the inside surfaces of the door and door frame. The switch is mounted on the door or window frame, and the magnet is placed on the moveable part of the door or window. If the door or window is opened, the magnet will no longer be in the proper position to hold the switch closed. This will open the switch, which breaks the flow of current to the control box, which in turn trips a relay and sets off the alarm.
Even though the most popular type of contact switch is surface-mounted, they also are available in a recessed version that is actually embedded in the door or window frame and hidden from view (see Figure 4). You typically find these in homes where the aesthetics are important. Most people are very sensitive to any kind of alarm wiring showing in their homes, which makes the recessed switch an ideal choice.
Contact switches are manufactured in various sizes and strengths, depending on the application. The size of the magnet generally corresponds to the strength. The bigger the magnet, the stronger it is; conversely, the weaker magnets tend to be small. Whether large or small, the application dictates the size and strength used. For example, the older the door or window that the contact switch is applied to, the more play it usually has. If there is too much play and the magnet strength is not adequate to compensate for the movement in the door, false alarms could result. On the other hand, if the gap between the door and the door frame is relatively small, a lighter-duty contact switch would be acceptable.
Contact switches are placed in the protection loop of the alarm system and act as the faucets that we described in the first chapter. When the magnet is holding the switch closed, the electricity is able to flow freely through the protection loop and back to the alarm master control box. However whenever the magnet is moved away, the switch opens and can no longer flow through the protection loop and back to the master control. This causes it to activate the bell or siren and, if the system is connected to a monitoring facility, alert the authorities.
Now the fun begins. Here is the 10-second circumvention technique. You won’t believe how simple it is to circumvent this very popular and widely used device. Keep in mind that the contact switch is a vital part of almost every alarm system ever installed. Even though this device is one of the simplest to defeat, it is still widely used.
Circumventing a contact switch is as simple as twisting two wires together. In fact, most of the circumvention techniques that we will look at involve twisting two wires together. The question is which two? In the case of the contact switch it’s easy, because there are only two wires going to the switch.
To completely remove that particular switch from the alarm protection loop, make sure that the alarm is off. If it is on, you will activate it by performing the following procedure.
At this point you may wonder how someone with ill intent could gain access to your system while it is off. A common method of accomplishing this task is called the “inside job”. No big mystery how this name came about. The most recent crime statistics show that employee theft is one of the biggest risks to an employer. When someone on the inside sets up an alarm system for a later attack, it can normally be done without being detected easily. The person usually knows interior traffic patterns as well as the general work habits of other employees, which aids in the act of circumvention not being discovered. Bypassing the alarm can also take place in a busy environment- if a merchant were distracted by a partner in crime, the circumvention could probably be accomplished successfully.
The same holds true for devious relatives who have had their selfish eyes on the family fortune. A home can be set up as easily as a business. Keep an eye on the in-laws. Do you know where your children are tonight? Repair people as well as other visitors could also be setting you up.
Now to the technique. Simply remove the two wires connected to the top of the switch. Strip off some of the insulation or any protective coatings so that the bare wire is exposed. Under normal conditions, only 6-12 volts DC run through the wires, so you won’t get a shock by touching them. Now twist them tightly together tightly and leave disconnected from the contact switch. By doing this, the alarm protection loop will not see the opening and closing of that particular switch. Why? As far as the alarm master control knows, the system is operating properly because it will receive the voltage whether the switch is opened or closed. Since the contact switch is no longer connected to the protection loop, the master control does not see it.
Look at Figures 5 and 6. In Figure 5, you see the contact switch connected properly. In Figure 6, it has been bypassed. This technique is so simple it’s amazing that more systems haven’t been circumvented this way.
This technique will address 99 percent of all typical alarm systems. There are a few situations where contact switches, when shorted as described above, will actually cause the alarm to activate. However, since the system is off, you will not be detected. The lesson here is to always conceal all wiring and contact switches when installing an alarm in your home or business. In most cases, surface-mount contacts can be installed in such a way that the wires are hidden in the window and door frames (the recessed version mentioned earlier). This will discourage tampering of your system.
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