Sleep mode

[Vikster]

Can I allow one person's call to ring out when my phone is on silent when I'm asleep in case of an emergency 

[Pugs1957]

Yes, you can do this using Do Not Disturb function.

[IndiW]

I have used Brixby Routine for this task
My phone goes to silent mode after 11pm (Brixby routine)

2nd - IF I were to receive a call from, A, B, or C, between 11pm and 5am, Brixby will makes my phone to Ring or turn off silent mode

[KevP79]

You can mark specific contacts as favorites and they'll be able to call when your phones on do not disturb mode. It's a handy feature really.

[Midge123]

I use Do not disturb and you can have contacts you can add to get straight through and if someone calls twice within a certain time they can get straight through to the phone as well like a emergency calling you I have the s20 ultra and used it for the last 2 years and more hope this helps you