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Wall-mounted electromagnetic door holder securing a door in the open position. An electromagnetic door holder (electromagnetic door holder and release or hold-open device, sometimes informally called a mag hold open or electric doorstop) is a simple electromechanical mechanism which can be used to hold a fire door or security door open until given a signal to release.
The EN 54 series of standards covers the following topics and product groups related to fire detection and fire alarm systems: [6] [7] Introduction: the introduction to the series of standards contains a diagram of a fire alarm system as well as numerous definitions of terms that are used in the other parts of the series of standards.
Idle signal is 24 V, periodically shortly pulsed to 0 V (pulses are not synchronous) in order for the receiver to ensure no shortcut to either 0 V or 24 V. Active signal is issued when both lines present 0 V; a single line presenting 0 V for a duration longer than the test pulses is sufficient to signal an event. Some related terms:
Alarm conditions can be explicit—for example, an alarm point is a digital status point that has either the value NORMAL or ALARM that is calculated by a formula based on the values in other analogue and digital points—or implicit: the SCADA system might automatically monitor whether the value in an analogue point lies outside high and low ...
A programmable logic controller (PLC) or programmable controller is an industrial computer that has been ruggedized and adapted for the control of manufacturing processes, such as assembly lines, machines, robotic devices, or any activity that requires high reliability, ease of programming, and process fault diagnosis.
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Remote alarm systems are used to connect the control unit to a predetermined monitor of some sort, and they are available in many different configurations. Advanced systems connect to a central station or first responder (e.g. police/fire/medical) via a direct phone wire, a cellular network, a radio network, or an IP path. In the case of a dual ...