Midfielder returns to north Essex.
Former midfielder David Fox returned to north Essex this week, and trained with the U's squad for the first time on Thursday morning.
Fox signed for the U's in the summer of 2009 and after twenty-one appearances, left for Norwich City twelve months later.
U's boss Tony Humes said of the agreement: "David has come down and is going to train with us for a while.
"It will be a good chance for us to look at him and him to look at us and we'll see what happens after that."