The Emergency Transfer Relay (ETR) feature provides basic telephony services in case of a power outage or failed connection to Communication Manager. ETR services are provided on the MM714B media module by connecting the module trunk port 5 to line port 4. You can also connect two external 808A ETR panels to the Branch Gateway front panel port. Each 808A Emergency Transfer Panel provides emergency trunk bypass or power-fail transfer for up to five incoming trunk loops to five analog phones. It also maintains connections when switching from Emergency Transfer mode to normal operation.