Operator Incoming Calls issue

[Siva chinap]

We're experiencing issues with the CP-7861/8800 operator phones with expansion modules. The operator receives incoming calls minimum of 5 to 6, every minutes. When they're on an active call and attempt to transfer, the notifications for incoming calls interrupt them, forcing them to clear all incoming calls to complete the transfer. This appears to be the default behavior of Cisco endpoints. While we're aware of a PC-based console solution, it doesn't meet our needs. Is there any configuration we can fine-tune on CUCM to adjust the notifications?
If not, are there any third-party SIP phones with expansion modules that CUCM supports?

[Nithin Eluvathingal]

What is your "Maximum Number of Calls" settings on the line ??

Have you tired increasing this value and verified the behavior ?

[Paul.Blackburn]

You could set the busy trigger to 1 and the maximum number of calls to be at least 2.

Once they are on a call, any callers will receive then receive a busy / engaged tone.

Maximum number of calls should be set to 2 or greater, otherwise they won't be able to transfer.

If you have multiple operators, use a hunt group to distribute the calls to them.