The codes are available at the RCA support website.
RCU300 - SystemLink 3 Television Programming Instructions
Find codes for your TV below.
Press and hold the CODE SEARCH button.
Press and release the TV button. Proceed to the next step after the Verification Light flashes.
Enter the three digit code from the TV list.
Release the CODE SEARCH button.
With the TV on, press another button, for example CHANNEL UP. If the TV responds, no further programming is required. If the device does not respond, repeat steps 2-5 using another code.