Nortel Networks 9150 - Manual (Page 49)

Remote Gateway 9150 Installation and Administration Guide 19
January 2005 Remote Gateway 9150 description
QoS Transitioning Technology
If the QoS on the IP network falls below a predefined threshold, you can
configure the Remote Gateway 9150 unit to automatically route voice traffic
away from the IP network connection to the PSTN connection. Refer to “QoS
Transitioning Technology” on page 34 for a detailed description.