Plantronics Cable 85638-01 (formerly 40287-05) is used with Plantronics EHS cords
such as APC-43
on some Cisco IP phone models or APP-51
on some Polycom IP phone models, or on some Grandstream phones where the headset port is located too far for the EHS to reach. It is ONLY
needed if you need longer cord length for your EHS, such as if you have a sidecar module.