Great value: The 24iC Mini Door/Window Sensor (TX-E201) is a compact, low profile (1/4″) contact that provides intrusion detection for application in homes and small businesses and include with both white and brown covers to match your decor. It can easily be installed on doors, windows, cabinets or other items that can be opened and closed. The TX-E Series Door/Window Sensor also contains a replaceable lithium battery that lasts up to five years under normal usage. • Works with Qolsys (IQ panels) and Interlogix (Simon, Concord, NetworX) systems. 319.5 MHz • Field proven wireless technology • Snap on, interchangeable covers (white and brown) • Case tamper • Replaceable battery with up to 5 years of battery life (based on usage)