Which frequency is not used for wireless security systems?

• A. 2.4 GHz
• B. 900 MHz
• C. 2.9 GHz
• D. 5.8 GHz

Answer: (C)

Wireless security systems choose frequencies that are widely supported for low-power, short-range devices, balancing range, penetration, and coexistence with other gear. The typical bands used are around 900 MHz, 2.4 GHz, and 5.8 GHz because there are many certified components and less regulatory hassle for residential sensors and panels. A frequency like 2.9 GHz isn’t part of those standard low-power, unlicensed bands used for home alarms, so it isn’t commonly employed in wireless security systems. It lacks the established ecosystem of devices and certifications, and would face more interference and regulatory hurdles, making it impractical for typical alarm setups.