My phone used to buzz all night. Group chats, news alerts, the occasional spam call, every ping yanking me out of sleep. I finally turned on Do Not Disturb, slept great for one night, and then missed a 6 a.m. call from my sister about our dad being in the hospital. Not her fault. My fault, for setting up the feature wrong. Do Not Disturb is not an all or nothing switch, and once I learned the settings, I got the quiet nights and never missed an important call again.

The key is favorites and starred contacts

Every phone lets you pick who can break through the silence. On an iPhone you mark contacts as favorites, and on Android you use starred contacts. Calls from those people ring normally even when Do Not Disturb is on. Take two minutes right now and add the people who actually matter: your partner, your kids, your parents, your doctor. That is the whole trick. Everyone else can leave a message.

Repeated calls are a built in safety net

Both major phone systems have a setting that lets a second call from the same number within a few minutes ring through. The logic is simple: someone calling twice in a row is probably not a wrong number, it is an emergency. If your mom calls twice at 6 a.m., you will hear it. Turn this on if it is not already. It has saved me more than once.

Schedule it, do not toggle it

The biggest mistake I made was treating Do Not Disturb like a manual switch I had to remember. The real power is scheduling. Set it to turn on automatically at your bedtime and off at your alarm. Mine runs from 10:30 p.m. to 6:30 a.m. every day, and I never think about it. If your schedule varies, use the sleep schedule feature or set it to end when your morning alarm goes off.

The exceptions that still catch people

A few settings sneak past Do Not Disturb and can still wake you. Timers go off no matter what, so if you set a cooking timer and forget it, it will ring. Alarms always ring, which is what you want. And if you have an Apple Watch or a similar wearable, the watch may vibrate for notifications even when the phone is silent. Set the watch to mirror the phone’s Do Not Disturb or you will trade phone buzzes for wrist buzzes.

One honest warning

Do Not Disturb will not stop a determined caller who has your number and tries ten times, and it should not. It is for the noise, not for hiding from people. If you genuinely need to be unreachable, that is a different setting entirely.

The morning my sister called, my phone was silent because I had set it to block everyone. Now it is silent for everyone except the short list of people who matter, and my dad is fine, which makes this whole story much easier to tell.