Busy Override feature
From Zenitel Wiki
| Feature: | Busy Override |
| Default directory number: | 58 - during conversation or M+M (Double M) |
| Feature number: | 61 |
| Parameter 1: | 0 (N/A) |
| Description: | During busy tone: Forces dialled station free, then connects.
During conversation press 58 to leave a Call Back message to the other station. |