hi have one of these with an outdoor sensor with it, had to change the batteries on the sensor as the clock was only recognising it when it was really close to the clock, the clock was ok as it was still speaking clearly etc so it was obviously the batteries on the censor, any how, now its got new batteries in it, its not recognising the sensor at all, do i have to pair it up or something, again, can't look for instructions on the web as i can't get on it!! help thanks trace