Audible Warning Devices (WDs) – Intruder Alarm Installation
The audible warning devices (WDs) are used in an intruder alarm system to generate an audible warning. When an intruder alarm system is in an active mode, it triggers all programmed outputs. The audible warning devices will start emitting an audible warning to alert people about the activation of an intruder alarm system.
The audible devices are connected to the system output, the panel sends a signal to the WDs and the devices will be activated. There are two types of audible devices: self-powered audible devices and remotely powered audible devices.
Self-powered audible device
A self-powered audible device is equipped with an internal source of energy to power the bell. In the event of the main power failure, it can still activate via a secondary power source. In most bells, a backup battery is used. The modern bell boxes comply with the British standard BS50131 and use rechargeable Ni-Cd batteries which are kept charged by the control unit. A self-powered audible device needs to comply with Annex C of PD 6662: 2004 and with all the other provisions of prEN 50131-1: 2004 relevant to WDs.
The code of practice (Sub-clause 8.1.4 of prEN 50131-1:2004) also emphasis that means shall be provided to recognise a fault condition in the alternative power source.
Remote powered audible device
A remote powered audible device has no internal power source and it is powered through a control unit. For this reason, when a remote powered audible device is installed, there should be at least two warning devices. In accordance with British standards, standby batteries should not be wired up in parallel because a failed battery may not be detected by the I&HAS.
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