Maybe I'm being a bit picky.
I was really pleased with this as it keeps my wife in contact with me since she has had to live downstairs following a severe stroke, and following a fall at 2 in the morning.
Everything is perfect, except I think the ON/OFF switch is a bit fiddly. I've got used to it now but can imagine someone with poor hand co-ordination finding it difficult.
AND (nothing to do with the operation of the units), despite checking the spec on this site and the manufacturer's site, nowhere did it say whether the system is mains or battery!!
(It's mains operated, by the way)