Mandated by federal law, all garage door openers include
features that stop the doors from crushing objects in their paths and
cause the doors to reverse direction if they strike something. In most
cases, this is controlled by an electronic beam that, when broken by
a person or object, triggers the safety mechanism.

All garage door openers produced today use "rolling codes"
for the greatest security. Each time the door is opened (using the remote
transmitter), a new, random code is generated. This prevents code theft
and ensures that a neighbor's remote control will not open your garage.