The XRO91P (it says XRO-91 on the back of the remote) is a 1-way transmitter for the Prestige XRO9100 System. There is also a 2-way remote for that system called the XRO92P (XRO-92.)
To open the remote simply take a coin and insert it into the opener groove. Then twist and the remote will come apart. Take out the batteries and replace them with new ones. Then put the remote back together. We use the Santronix Keyless Entry Tester because we like to hear what the signal sounds like. It's really helpful for identifying bad remotes when you have a good one to compare it to.