... pic,record functions 4)2 indoor unit to 4 outdoor 5)1 indoor unit to 4 outdoor Silicon two ... and outdoor machine free form 1 to 1, 1 to 2,2 in 1, 2 to 2, 2 to 4, to meet the needs of different users ... lock, surveillance and night vision and other functions, to visit outside the doorbell, visual indoor machine ring ... lock automatically open, there is no need to go to the door to open, if the room no answer, ...