There are many 'big button' telephones around that claim to be good for the elderly, and the few that I've tried (and many more that I've read up about) have always come up short. But this phone actually does the job, thanks to two small features that are barely even documented but are - I think - crucial.
First, the two indents in the phone's base for the handset are nice and deep. That means that you practically push the handset *into* the base to hang up a call, and it has a satisfying tactile 'clunk' to tell that it's back in place. To an elderly person with poor eyesight and/or poor spatial awareness, this is hugely important as it means no more accidentally leaving the phone off the hook.
Secondly, it has a volume boost facility that can be *permanently* engaged. Lots of phones have volume boost, but you usually have to press the boost button *after* the handset has been picked up. To an elderly person who gets confused about buttons and their functions, that's an added confusion that means that the boost often won't get used. But with this Geemarc phone, there's a little switch on the back that allows the boost facility to be permanently engaged so that it gets used every time.
There are other added benefits too, like no need for batteries or a mains power supply - the boost facility works off the phone line voltage, and it really does work well. (The phone can take batteries, but that's just to increase the ringer volume which I found totally unnecessary as the ringer is perfectly loud enough already.)
In summary, a robust phone with excellent audio quality that really meets the needs of an elderly person.