See also:

Volume control buttons
Models without Hands-free system Models with Hands-free system Press the “+” button to increase the volume. Press the “−” button to reduce the volume. A number indicating the volume ...

When “CHECK DEVICE” is displayed
This message is displayed under the following conditions. - When there is a short in the USB bus - When a non-corresponding device (for example a USB mouse) is connected - When a non-correspo ...

Certification for the Handsfree system
FCC WARNING Changes or modifications not expressly approved by the party responsible for compliance could void the user’s authority to operate the equipment. NOTE This device complies ...