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  2. Dual loop - Wikipedia

    en.wikipedia.org/wiki/Dual_loop

    Dual-loop is a method of electrical circuit termination used in electronic security applications, particularly modern intruder alarms. It is called 'dual-loop' because two circuits (alarm and anti-tamper) are combined into one using resistors. Its use became widespread in the early 21st century, replacing the basic closed-circuit system, mainly ...

  3. Security alarm - Wikipedia

    en.wikipedia.org/wiki/Security_alarm

    In the event of an alarm, the premises control unit contacts a central monitoring station. Operators at the station take appropriate action, such as contacting property owners, notifying the police, or dispatching private security forces. Such alerts transmit via dedicated alarm circuits, telephone lines, or the internet.

  4. List of projects published in Radio-Electronics magazine

    en.wikipedia.org/wiki/List_of_projects_published...

    This circuit can be programmed for step up, step down, positive, negative, voltage and current regulation. Robert Frostholm 51/2 February 1980 Not just another digital clock [2] 5 + 1 ⁄ 2-inch high single-digit LED readout makes this clock unique. John D. Warobiew 51/2 February 1980 Automotive burglar alarm [3] Build it for less than $20.

  5. Passive infrared sensor - Wikipedia

    en.wikipedia.org/wiki/Passive_infrared_sensor

    This relay completes the circuit across a pair of electrical contacts connected to a detection input zone of the burglar alarm control panel. The system is usually designed such that if no motion is being detected, the relay contact is closed—a 'normally closed' (NC) relay.

  6. Standards for Alarm Systems, Installation, and Monitoring

    en.wikipedia.org/wiki/Standards_for_Alarm...

    The alarm transmission methods covered under UL 365 can be categorized under standard line security or encrypted line security. The systems are required to operate within the limits of Class 2 remote control and signal circuits as defined by the National Electrical Code, NFPA 70. [15]

  7. Electric bell - Wikipedia

    en.wikipedia.org/wiki/Electric_bell

    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.