Line Powered Off Hook Ring Mw Indicator

How big is the light on this device? There is a light on phone that is left off hook but it is too small for someone with macular degeneration.

Will only one work for all of your phones or do you need multiple devices for each phone to detect which phone is not hung up?

How does this connect to the phone. Thank you.

Would just work with your landline if you have a 911 Guardian alert system setup with your phone?