I believe HHC being a feature dependent on the phone firmware version. As it has to be enabled on CUCM, there came some doubts about my thinking and as I am unable to verify at the moment, I would like to ask if HHC being supported on Cisco Unified Communication Manager EXPRESS at all!?
Headset Hookswitch Control is only available on 7942, 7945, 7962, 7965 and 7975 Cisco IP Phone models.
Headset Hookswitch Control is available for SCCP and SIP
Fully supported under CME
Enabled via service phone CLI under telephony-service by entering âphone ehookEnable 1â.
UC520-120(config-telephony)#service phone ehookEnable 1