Search results
Results from the WOW.Com Content Network
Sensors: In a security alarm, some sensors detect intrusions. Sensors' locations are at the perimeter of the protected area, within it, or both. Sensors can detect intruders by different methods. Alerting devices indicate an alarm condition. Most commonly, these are bells, sirens, also and or flashing lights. Alerting devices serve the dual ...
The self-test feature can be used a maximum of 60 times for optical sensors and 100 times for heat sensors, which equates to an expected life of up to 14 years of optical detection self-testing, and 20 years of heat detetection self-testing, with an expected maximum of 4 self-test and 4 manual tests a year, before the detectors need to be replaced.
A typical volume of Bell System Practices from the 1970s. The Bell System Practices (BSPs) is a compilation of technical publications which describes the best methods of engineering, constructing, installing, and maintaining the telephone plant of the Bell System under direction of AT&T and Bell Telephone Laboratories. [1]
Door and window sensors are also implemented in most home security systems. One part of the system is installed on the door or window itself while the other part is installed on the frame of the door or window. The two part system connects securely when a door or window is closed, creating a security circuit. [5]
Fire alarm bell. Fire alarm bells are divided into two categories: vibrating, and single-stroke. On a vibrating bell, the bell will ring continuously until the power is cut off. When power is supplied to a single-stroke bell, the bell will ring once and then stop. It will not ring again until power is turned off and on again.
Discover the latest breaking news in the U.S. and around the world — politics, weather, entertainment, lifestyle, finance, sports and much more.
Get AOL Mail for FREE! Manage your email like never before with travel, photo & document views. Personalize your inbox with themes & tabs. You've Got Mail!
A doorbell is a signaling device typically placed near a door to a building's entrance. When a visitor presses a button, the bell rings inside the building, alerting the occupant to the presence of the visitor. Although the first doorbells were mechanical, activated by pulling a cord connected to a bell, modern doorbells are electric, operated ...