I've just replaced a Philips twin ( base and second phone) by a Panasonic. Just wondered if I could set up one of the Philips handsets to work with the Panny, but Philips requires a registration code ( shown on bottom of Philips base unit) and AFAICS there is no code anywhere in Panny instructions etc.
Perhaps my thinking is odd.. why buy a twin when you want triple..... but third phone would only get occasional use not worth the extra cost but a bonus.