Chamberlain 2000SDC-R - Manual (Page 29)

Children operating or playing with a garage door opener
can injure themselves or others.
The garage door could
close and cause serious injury or death. Do not allow
children to operate the door controls or remote controls.
A moving garage door could injure or kill someone under
it. Activate the opener only when you can see the door
clearly, it is free of obstructions, and is properly adjusted.