Please refer to the Plantronics Compatibility Guide for the correct cable

Electronic HookSwitch (EHS) communicates electronically with the phone, eliminating the need for a HL10 lifter

Avaya IP 1608, 1408, 1416, 1616, 2410,4630,5410, 6416D+M, 6424D+M, 9404, 9406, 9408, 9504, 6508, 9608, 9610, 9611, 9611G, 9620, 9620C, 9620L, 9621, 9630, 9630G, 9640, 9641, 9641G,9650, 9650C, 9670 EHS Cable for CS500-Savi 700