2.4GHz digital frequency hopping and encryption technology transmission distance up to 200m at open area robust anti-interference; Has the infrared night vision clear visual doorbell can monitor and photograph motion detecting to record the images in the dark; Indoor machine adopts 7 inch colorful LCD display to image; The door machine has tamper alarm settings rainproof function; Hands-free calling and intercom open electric lock button; Indoor machine built-in 16 chord rings so you can choose the bell; Indoor machine can display the date and time; Indoor machine can be active and automatic take pictures and pictures record picture time it can automatically saved to the SD card; Support for human motion detecting function it can be set to detect sensitive. When objects move in monitoring range the indoor machine will open the video function. If 30 seconds without any buttons it will enter sleep mode. Support motion detection. When the visitor comes close to the peephole within 1.5m the indoor monitor will start to work and take one photo soon. If no action is taken for 10 seconds after that it will enter into sleep mode; Brightness and talk volume are adjustable; One indoor machine can be monitored at most four door machine four door machine can be set to the doorbell or monitoring video four images can recorded at the same time.