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 (EU24) 2420, 4610, 4610SW, 4621, 4621SW, 4622, 4622SW, 4625, 4625SW, 4630, 4630SW, 5420, 5610, 5620, 5621. EHS Cable for CS500/Savi 700