Digistats are 'paired' you have a receiver and and a sender, they run at 233 gigahertz, you can have a situation where they become mis-matched, if you have removed the batteries, you have to go through a learning procedure, if you do not have the paperwork, you can download instructions from the drayton website. If the learning/pairing fails, I am afraid you will have to purchase two new units.
Dave, May 2010