On Wed, 31 Jan 2018 21:03:51 +0000, Chris Green wrote:

Has anyone come across a video door entry system which uses an
existing television for the display? My M-I-L wants a door entry
system which allows her to see the visitor before unlocking the door
but any 'extra' display hardware really isn't practical.

Display on mobile phone is no good because it probably won't be to
hand and is too small (so she'd need to find her glasses as well as
the phone). A dedicated display doesn't make much sense either,
there's really not space for it anywhere.

It would make *much* more sense to be enable to interrupt the TV
display, it's always on and the *important* thing is that it's when
M-I-L is in easy chair in front of the TV that it takes her a long
time to get up and get to the front door.

Any ideas anyone?
MIL used to have one, it was supplied by Social Services (free to
her). Cam mounted on wall above and to side of door (outside). Cable
plugged into a wallwart psu and another cable plugged into the back of
a scart plug which in turn went into the TV. As said by others, she
has to know how to switch to another input on the TV and back again.