The receivers allow you to monitor up to 8 different STI wireless alert devices at a single, convenient location. Supervised for low battery and signal reception, they have an audible chime tone or 12 VDC output for siren. The 4-Channel Voice Receiver sounds a tune or a prerecorded programmable voice message. Offers ten tones/tunes or 53 selectable words (English or Spanish) to create a custom message up to four words. The 8-Channel Receiver offers a mirror function that can work with up to four additional 8-Channel Receivers. Devices can be latching or momentary by zone. STI offers multiple wireless products designed to alert you of several different conditions (such as: an open garage door, mail delivered, a car in the driveway, open exit door, removed fire extinguisher or activated push button, etc.).