Plantronics 26716-01 cable is the bottom coiled cable that plugs between the Plantronics H-series headset and Plantronics M12, M22, M10, or MX10 amplifiers. The 26716-01 is also used as a direct connect solution when you plug any Plantronics H-series headset into a Cisco VoiP telephone. When used with the Cisco telephone, no amplifier is used.