Burglar alarms work by using electrical circuits and sensors to detect intruders. There are types of burglar alarms including motion detectors, which identify changes in position in a specific area, and smoke or fire alarms, which detect possible arson. There are also panic detectors which detect movement changes in a particular area.Know More
A basic burglar alarm contains an electric circuit connected into an entryway, with a switch that opens or closes the circuit. The switch detects acts of intrusion such as opening a window or door. This kind of alarm is built into an entryway. It is classified into two categories. The first is an open-circuit system, in which the circuit is closed and electricity flows when the door is opened. Completion of the circuit triggers the alarm. The second type is a closed-circuit system, wherein the circuit is closed when the door is shut. The circuit opens when someone opens the door, thus triggering an alarm.
In some burglar alarms, sensors are attached to a central unit that sends out a signal upon identifying any intrusion, fire or panic. Signals are typically sent in the form of loud noise. Modern burglar alarms send signals through the Internet or via telephone lines. The homeowner becomes alerted whenever a possible intrusion is identified. Typically, advanced alarm systems send an automated email or phone call to inform a person of any suspicious activity at home.Learn more in Doors, Windows, & Locks
Automatic doors are able to detect persons, and open at the appropriate time, through the use of automatic sensors. There are many types of sensors that are used on automatic doors.Full Answer >
An electromagnetic lock creates a magnetic field when energized, causing an electromagnet and armature plate to become attracted to each other strongly enough to keep a door from opening, according to YLI Electronics. In most cases, the armature plate is on the edge of the door, while the electromagnet is wired to the building's power grid in the wall next to the door frame.Full Answer >
Telegraph keys are switches in electrical circuits that power on the current. When the operator taps out the signals for a word, the switch finishes a circuit, permitting electricity to continue around it. At the other end of the line, the recipient watches a pointer or dial indicating the different patterns of code, listens to a buzzer or reads the print out from a device.Full Answer >
A pull shade is made using fabric, a wood dowel or aluminum tube, a small wood slat, a beaded chain, an iron, iron-on shade material and a shade clutch. Pull shade kits are also sold at local hardware stores and include all of the necessary pieces to build a pull shade.Full Answer >