Volume and handset override
From Zenitel Wiki
Volume and handset override is applicable for analog display stations and all types of IP stations. Analog stations without display does not support handset and volume override.
Volume and handset override is activated by the following features:
- Group calls with Alarm priority
- Remote setup of audio program to group, using feature code 75, event handler command PRG, or ACDP command $PROG. The audio program must have the flag Handset/Volume Override enabled.