I'm working w/ a 2006 Chamberlain AccessMaster 1/3 HP M350 garage door opener rated at 120VAC 5A 60Hz. This particular garage door opener provides three (3) contact points (screw terminals) on the back for hardwired signaling (e.g., push-button momentary switch, safety reversing sensor, etc.)

Screw terminals 1 & 2 are for 2-wire, 24V low voltage wiring to wall-mounted controller. Terminals 2 & 3 are for safety reversing sensor pair (IR beam "eye") mounted at the base of garage door tracks.

(Note: My model utilizes the single push button controller. The more expensive model in this manual uses the 3-button controller.)