First Alert ACTION T-1000 - Manual (Page 80)

installing an Interface
Inserting the interface board
1. Locate the connector cover at the back of the upper case, shown in
the illustration below. Push it down and in, toward the inside of the
printer, until it clicks. You need to move the cover to allow access to
the new interface connector when the case is reassembled.
2. The screw marked CG at the rear of the circuit board is the
connection for the frame ground wire. Unscrew it and then use it to
connect the frame ground wire as shown below.
A-6 Appendix