Nokia Phone Adapter HDA-8 Use with compatible TTY/TDD devices and headsets only  Check your TTY/TDD device to ensure that the connection is compatible  Nokia original headsets attach directly to the phone and do not require adapters.  *Note: This Adapter has 2.5mm jack to allow you to use any of the universal 2.5mm headset such as Jabra, Plantronics or any other major manufacturer.