The Emergency Transfer Relay (ETR) feature provides basic telephone services in the event of system failure, such as a power outage or a failed connection to the MGC. An external 808A ETR relay panel can be used in conjunction with an analog media module (MM711, MM714, MM714B, or MM716). The ETR panel provides up to five incoming Central Office (CO) trunk loops to five selected G450 analog lines. Thus, one ETR panel supports up to five emergency lines. You can cascade a second ETR panel, providing support for up to 10 emergency analog phones. ETR is activated automatically upon system failure by closing the tip/ring contacts between the analog lines and the analog trunks. When ETR is activated, all calls are directed by the analog relays between the outside lines and the analog telephones. A current-loop detection circuit prevents ongoing calls from being disconnected when normal functioning resumes. If a call is in progress on an outside line when the problem ends, the call continues.The trunk port and analog line port passing through the ETR panel do not start to operate until the active call ends.

In addition, each MM714B media module installed in the Branch Gateway can provide identical ETR services in the event of system failure by connecting trunk port 5 to line port 4. You can install an MM714B media module in any slot. When ETR is active and the Branch Gateway has power, the ETR LED is lit.