used them like watch dogs." But crickets work in the opposite manner of watchdogs. A dog barks when it detects an intruder. A cricket stops singing when approached by an intruder. The crickets are kept in decorative cages resembling bird cages. These cages are placed in contact with the floor. During the day, the house is busy with normal daytime tasks. When things quiet down at night, the crickets start singing. If someone comes into the house at night, the floor starts to vibrate. "The vibration frightens the crickets and they stop singing. Then everyone wakes up --- from the silence. The family is used to hearing crickets at night and knows something is wrong if the crickets aren't singing. A similar observation was made in England about millers who lived in their mills. A mill wheel makes a great deal of noise, but the miller only awakens when the mill wheel stops turning. Driveway alarms Driveway alarm systems can be combined with most security and automation systems. They are designed to alert residents to unexpected visitors, intruders, or deliveries arriving at the property. They come in magnetic and infrared motion sensing options. Driveway alarms can also be purchased in hard-wired and wireless systems. They are common in rural security systems as well as for commercial applications. Electro-mechanical (shaker) sensors These electro-mechanical devices are mounted on barriers and are used primarily to detect an attack on the structure itself. The technology relies on an unstable mechanical configuration that forms part of the electrical circuit. When movement or vibration occurs, the unstable portion of the circuit moves and breaks the current flow, which produces an alarm. The medium transmitting the vibration must be correctly selected for the specific sensor as they are best suited to different types of structures and configurations. This technology is gradually being replaced by intelligent digital accelerometer-based systems. Advantages: Low-cost and easily installed on existing fences. Disadvantages: Must be fence-mounted. Being mechanical in nature, the system is unable to analyze differences in the pattern of vibrations (for example, the difference between gusts of wind and a person climbing the fence). MEMS Accelerometer MEMS technology, Micro Electro-Mechanical System, is an electromagnetic device that is created using the same technologies used to produce chips: this technology is called photolithography, incision and ionian implantation. The result is a very compact and small device that has dimensions of 4x4 mm, 1,5