monito r and shabbat

Question

the monitor that eitan is referring to is extrememly popular. almost all monitors sold today have this feature. to explain : Assume the volume was on mute, it has a series of lights (let's say 5 in a row) and if there is a light cry 1 - 2 lights would flash on, if there was a loud cry or noise 3,4 or 5 light would flash on. evn if the volume is on, these lights would flash. IS the baby monitor still permitted on shabbat??