Internal sounder are a useful addition to any burglar alarm system. Piezo sounders are relatively inexpensive and will effectively disorientate an intruder inside your property.
Piezo sounders replicate the external sounder and are connected in parallel to the external sounder circuit. Extension speakers replicate the existing internal speaker or in the case of blank end-stations the tones orf the RKP (Remote Keypad).
These Piezo electronic sounders are designed to be fitted internally and connect into the same circuit as the external sounder in a burglar alarm system and as such behave in the same way. They are a useful deterrent in that the intruder is disoriented by the loud noise inside the premises. They are available as a simple unit - Sound bomb I and II or in more attractive cases with in some cases integral strobe lights. In general they should be fitted away from the control panel so as not to indicate where the control panel is situated.
All major burglar alarm control panels have the facility to connect an internal extension speaker or in the case of a stand-alone control panel (where one is usually already fitted in the panel) to add an additional speaker. The speaker replicates the tones given by the existing speaker or those of the remote keypad - if fitted. They must be fitted to the dedicated speaker terminals on the panel and NOT to the external sounder terminals.
Sirens are electromechanical devices which are significantly louder than the more common piezo sounders. They find use in larger premises such as warehouses. The Masterblaster has an extremely loud sound output of 127dB - the hearing pain threshold is 120dB. The Masterblaster is a mains-operated device with an integral 12v relay which allows it to be fitted to any hard-wired burglar alarm control panel.