JPL EHS-5 EHS adapter

RJ-45 (8P8C) to 5-Pin Plug, RJ-9 (4P4C) to 2.5mm Plug (3 poles)
Electronically connects your DECT headset base to your telephone
Enables remote operation, answer/end calls, for wireless headset use with various phones, thus eliminating the need for a mechanical handset lifter