Comcast has 4 digit Remotes and 5 Digit remotes. The only way to tell, other than entering codes, is to look at the center button labeled "OK / Select." If it is Red, it is a 5 digit remote. If it is Grey, it is a 4 digit. I have found the 5 digit remotes have better support for new devices like combos and bluray players. Which remote do you have?

[Link: comcast.com]

^^^^^ 4 Digit Support

5 Digit Westinghouse : 10885 10889 10890 11282 11577