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LED Flash for Alerts
In Contacts, choose a contact, then tap “vibration.” If you don’t see vibration in the contact info, tap Edit and add it.
If you’re already editing a contact, tap “vibration” and then tap Create New Vibration. You can also go to Settings > Sounds > Vibration > Create New Vibration.
Go to Settings > Sounds > Vibration and choose a pattern.
If you can’t hear the sounds that announce incoming calls and other alerts, you can have iPhone flash its LED (next to the camera lens on the back of the iPhone). This works only when iPhone is locked or asleep. Available for iPhone 4 or later.
Turn on LED Flash for Alerts: Go to Settings > General > Accessibility > LED Flash for Alerts.