The HELIX key fob allows you to arm and disarm the basic system but is ready with additional features if you choose to expand your security system to include home automation. FEATURES: Tactile button click and LED blink for feedback. Recessed buttons for no “pocket false alarms”. Full pivoting built-in key ring tangle-free storage. Strong, reliable RF signal. 4-6 year battery life, on A27 battery. 2.5 x 1.3 x 0.55 inches.