We have the Cisco SPA 525G2 phone and are using it with the Savi700 series or CS500 series headset with the APC-45 EHS cable. We have enabled EHS on the Cisco Call Manager but cannot get call control. How can I solve this issue?
The SPA525G2 phones are only supported with Cisco Call Manager Express.
This is a known issue: EHS not working in SCCP mode for SPA525
EHS currently works in SIP mode only for the SPA525. This issue will be fixed by Cisco in Firmware 7.5.4