2. What happens if a phone call comes in while the E18 is connected to the phone via USB?

A: According to current tests, some smartphones will not play voice calls through either the phone's earpiece or the E18, while others play voice calls through the phone's earpiece, switching to the E18 if speaker mode is enabled.  The behaviour is not consistent owing to different Android implementations by different manufacturers.  Users are recommended to try different options (including speaker mode) in test calls and disconnect the E18 for voice calls if necessary.