You can use any of these as a switch:
- An external adaptive switch. Choose from a variety of popular USB or Bluetooth switches. 
- The iPhone screen. Tap on the screen to trigger the switch. 
- The iPhone FaceTime camera. Move your head to trigger the switch. You can use the camera as two switches; one when you move your head to the left, and the other when you move your head to the right. 
- Add a switch and choose its action. Go to Settings > General > Accessibility > Switch Control > Switches. 
- Turn on Switch Control. Go to Settings > General > Accessibility > Switch Control. 
- Turn off Switch Control. Use any scanning method to select Settings > General > Accessibility > Switch Control. 
- Bail out! Triple-click the Home button at any time to exit from Switch Control. 
 iPhone
iPhone