YSK: On iPhone, even if you have your phone on silent and Do Not Disturb, you can allow calls through from selected numbers, e.g., family, close friends, all while still blocking pesky emails and app notifications. Contacts > Click name of contact > Edit > Ringtone > Tick "Emergency Bypass."
from /r/YouShouldKnow
YSK：在iPhone上，即使你的手机处于静音和免打扰状态，你也可以允许来自选定号码的电话通过，例如，家人、亲密的朋友，同时仍然阻止讨厌的电子邮件和应用程序通知。联系人 > 点击联系人的名字 > 编辑 > 铃声 > 勾选 "紧急绕过"。