The Monnit ALTA Wireless Voltage Detection sensor is a compact and efficient device that detects the presence or absence of voltage in electrical systems. Operating within a range of 24 to 500 VAC, this sensor is ideal for monitoring HVAC systems, sprinkler systems, sump pumps, and other electrical appliances. It features a coin cell power source and operates at a frequency of 900 MHz. The sensor measures 1.1 inches in height, 2 inches in width, and 0.9 inches in depth, making it easy to install in various locations. It triggers alerts based on voltage state changes, displaying results as either 'No Voltage' or 'Voltage Detected'.