Do not buy it, guys... it doesn't always work, it has a mind of its own. Let me explain... the internal unit has a touch display with buttons that don't always respond and have a slow reaction time. The external unit has a good camera, but if someone presses the button, the internal unit takes a while to respond and it takes several seconds for the screen to turn on and "get going" so you can press to open or speak. Especially if the visitor presses the button again before you respond, the internal unit restarts and "starts from scratch" with the delay we mentioned. Specifically for me, since I installed it (2 years ago in a new house), at times the door opening doesn't work or it may work after many button presses, and lately the speaker of the external unit often buzzes and you can't communicate with the visitor. I don't have experience with other intercom systems, but this one has been frustrating for me and to be honest, if it didn't have these problems, I wouldn't mind its slowness. It reminds me, so you can understand, of the first smartphones that were slow, but back then it didn't surprise us because everything was like that... today, however, it's unpleasant for an electronic device to be so slow