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

For Cisco – 6945, 7821, 7841, 7861, 7942G, 7945G, 7962G, 7965G, 7975G, 8811, 8841, 8851, 8961, 8961, 9951, 9971