STI-3551 Wireless Entry Alert® Sensor

The STI-3551 is a transmitter and magnet only, not a complete alert system. It is part of Safety Technology International's 2015 Musical Wireless Chime Series and is meant to be added to that system, where the chime unit is what actually sounds. If you have no chime receiver yet, order one along with the sensor.

That is exactly what the STI-3551 is for. It is an additional transmitter and magnet for the 2015 Musical Wireless Chime Series, so a property manager or shop owner already running one chime can bring a back door, stockroom door, or side entrance onto the same system by adding sensors rather than buying another complete kit.

Door movement, not motion. The STI-3551 is a two-piece magnetic contact: one half is the transmitter, the other is the magnet, and the chime sounds when the two are separated. Traffic walking by an open doorway will not set it off, so it is the wrong choice if you want to catch people entering a room with no door to break contact on.

Output on the 2015 Musical Wireless Chime Series runs 64 dB to 88 dB measured at 1 foot, with the level depending on which of the sounds is selected. At the top of that range it carries through a normal retail floor or front office. In a running machine shop or an equipment room, plan on placing the chime close to where staff actually stand rather than relying on it from across the building.

No wiring runs to the sensor. The STI-3551 is a wireless transmitter paired with a magnet, which is what makes it practical on a leased storefront, a tenant unit, or any opening where you are not going to pull cable through a finished frame.

Ten sounds are selectable, and they are changed with the push of a button rather than a dip switch or a programming sequence. That matters where more than one alert device is running in the same space, since a tone nobody else on site is using keeps staff from ignoring it.