The STI-V34600 Wireless Doorbell Button Alert lets you know when someone is at the door. When the button is pressed it sends a wireless radio signal to the indoor voice receiver, which will sound a tone/tune or programmable voice message letting you know someone has arrived. If the supervised transmitter is removed from the door, stolen, loses signal or battery is low, the receiver will produce a single beep once a minute. Sensor uses one 3 volt lithium battery (included), with an average life of 5 years in normal use.
Everything you need to know about the STI 4-Channel Voice Receiver