Clear-Com HX System Frames - Manual (Page 109)

Figure 42: T1 Trunking using a E1 Network
8.6 Trunking failover
Where the E1/T1 trunking has been configured with redundant trunks audio will be switched
from the primary trunk to the backup trunk when a failure is detected.
When failover occurs from primary to backup there will be a three second audio break on
any route running over the trunk.
If the trunk routing is later switched back from the backup trunk to the primary trunk there will
be no loss of audio.
109 Eclipse HX-Median User Guide