Keep display on during a call
Samsung in their infinite wisdom decided that during a phone call the phone display should turn off and the phone lock. This is to save battery however it assumes you are holding the phone to your face. The setting for disabling this 'feature' doesn't work. Hence if you are on a conference call and have your phone on mute a lot, you have to unlock your phone, and then find your phone app to unmute in order to respond.
This also interferes with GPS navigation if you receive a call during a trip. If you answer the call, the phone will lock after a few moments on the call, and then you can't get back to your navigation without having to pull off the road or try to type your passcode while driving (dangerous and illegal).
New Application 'Keep Screen On' will allow Samsung users to override the behavior of turning off the phone when specific apps are running
By default it only shows downloaded applications however there is an open to show all apps including system programs.
Caveat: This workaround creates another problem in that if you complete your call and do not either turn off the phone or switch to another app - the display will stay on and drain the battery. So you need to be careful in using app, and which apps you override the display settings on, as this assumes you are now managing your screen usage for any apps overridden rather than allowing the system to manage it for you.