How do I get the system to pick up the signal again

Ali, November 2009

you now need to re bond the room stat which is the (transmitter) to the boiler(receiver) , by using the thermostat makers instruction booklet.
you would have ample time to change the batteries before this happened as a flashing battery sign would have been showing on the thermostat display for a fair bit before signal failure.

wirecutterman, November 2009