It is a simple disc pattern that just covers a small area in the bottom right portion of the screen...in the shape of a tadpole.
When I first got the CTX, I used the tadpole pattern because I used it on the eTrac a lot. The more I used the CTX though, the more I felt that it that takes away from one of the best features of the CTX, and that is using the tone bins in combined mode instead of using a disc pattern. I run a wide open pattern and use the tone bins to determine whether to dig or not. I realize that in some situations, that would be a audio/brain overload but it's all in what you get used to and I have gotten used to hunting that way.