Paging a phone set the phone to auto answer and open the speaker.
How can I set the phone to turn on just his microphone and the camera, if available, for security remote controlling?
Sam, you need to provide _way_ more information if you want a helpful answer. You haven’t even told us what type of phone equipment you’re using!
Given that this type of feature will be specific to the model in use (and not necessarily to Asterisk), that type of information is of primary importance for getting a useful answer.
In a general sense I would recommend you look at whether the equipment you are using can be commanded via specialised header to set speaker volume to zero.
Alternatively create a conference room that both endpoints get dropped into, but only the monitored end has ‘speaker’ privileges.
Or just press mute from the callers end (and don’t forget the disable the guard tone at the remote end; again dependant on your equipment).