Each line can support multiple calls. By default, your phone supports two active calls per line, and a maximum of six active calls per line. Only one call can be connected at any time; other calls are automatically placed on hold.
The system allows you to configure maximum calls/busy trigger not more than 6/6 both for SCCP and SIP. Any configuration more than 6/6 is not officially supported. For SCCP, you must upgrade to Cisco Unified CM 8.6 or above to support multiple calls per line.
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.