Door and Window Alarms
Most door and window alarms rely on a magnet attached to the door or window and a sensor which connects to the central control box attached to the sill or doorframe. When the home alarm is armed, the sensor passes a small electrical current to the magnet. The magnet acts as a conductor across the tiny distance and returns the current. Only when the current is not returned, such as if the door or window were opened, does the alarm sound. By passing a length of foil through the seam in a door or window, the foil does the same job as the magnet. The alarm will not sound when the door or window is opened so long as the foil is kept pressed against the sensor.
Effective Brute Force Methods
The average alarm system has externally placed sirens, and runs off the home's electricity. To that effect, the wire connecting the siren to the control box can be cut. Likewise, the power supply to the home can be severed. Most alarm systems have an internal battery, but they seldom last for more than thirty minutes before running down. If the burglar is impatient, he can simply break a large window and enter in that manner provided he does not disturb the magnetic sensor on the frame.
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ADT Wireless Alarms
ADT wireless alarms are among the best on the market. They have long-life rechargeable batteries, sensors to register breaking glass, an internally placed siren, and automatically use the home's phone line to call an ADT response center, which will then call the home and ask if police assistance is required. Regardless of how a burglar attempts to gain entry, he's going to set off the internal siren. However, if he's quick and knows what he wants, he might risk it. Home and car alarms are frequently set off by the owner, and it's rare for them to be taken seriously because of this. All the burglar needs to do is cut the home's phone line before attempting to gain entry, thus preventing the ADT system from notifying anyone of the break in. The burglar will know it's an ADT wireless system being used, as most homes who have them advertise it with the ADT logo near the front door. It might be meant as a preventive measure, but a burglar who sees that logo will know exactly what to do.