You can easily attach the Door Knocking Sensor (Model CA-DX, sold separately) to this hanger and hang it on your door knob to detect the knocking on your door. The CA-DX sensor sends a wireless signal to trigger the CA-360 to alert you that someone is at the door. Ideal for both home and hotel stay applications.
Operating Frequency: 2.4 Ghz
Operating Range: Up to 210 ft, open space
Battery Type: Two AA size alkaline (user provided)
Battery Life: Up to 10 months
Operating Temperature: +10 to +30°C
Size: 2.5” x 3.8” x 1” Wt: 4 Oz