The 29-year-old penned a one-year deal to become the club's second signing of the summer and joins in time to start pre-season training with his new team-mates on Thursday morning.
Cox told iFollow Iron: "I've known Harry for a long time from his Crewe days. He had a good career there and throughout his time playing we've stayed in touch really, and always had chats after games when our paths crossed playing against each other.
"When I realised he'd come available I was straight on the phone to him. He had a couple of other options but we've got it over the line and I'm delighted he's in the football club.
"He's an experienced campaigner and is good around the place. He's a really good talker on the football pitch, organises people and has a will to win - that's what I want throughout this football club.
"He's a really nice lad but when it comes to 3pm on a Saturday he's ready for a fight. He can do the horrible side of League Two well but when it's time to be calm, he can play too.
"He knows Alex (Kenyon, our first summer signing) and had a really good season with him last year. He also knows Myles (Hippolyte) from his days in Scotland with St Mirren.
"I've known him for a long time and have seen his career grow, and he was another one I wanted in this football club desperately, and over the last five weeks we've been trying to get it over the line."
Cox concluded: "They're the first two we've brought in and now we go onto getting the next one over the line. We're close, and I want to bring in what I feel is right for this football club, and what will turn us into a better squad, a better team and get better results.
"I have to make sure they're the right characters and players for this club. I'm really looking forward to Thursday and meeting with the boys again, and telling them how we're going to do it this season."
See much more from Neil Cox and Harry Davis on iFollow Iron.