I have a customer with a CallManager 7.X and a number of 6921 phones.
I'm trying to increase the "busy trigger" to allow for call waiting functionality, however I can not edit this field on the line configuration on that phone.
Isn't this phone supposed to support call-waiting?
Sadly, this model does not support multiple calls per Line or
traditional Call Waiting;
The Cisco Unified IP Phone 6921 supports two lines and offers a full-duplex speakerphone for a more productive, more flexible, and easier-to-use endpoint experience. The Cisco Unified IP Phone 6921 supports single-call per-line appearance, offering traditional telephony-like user experience for customers who seek this type of call interaction for their users. Fixed keys for hold, transfer, and conference; tri-color LED line and feature keys also make the phone simpler and easier to use.
You could leverage the second Line and Call Forward Busy on Line 1 to
build a simulated Call Waiting for your users