Each ISDN port on the MM720 and MM721 media module supports up to two ISDN BRI stations.

You cannot administer MM720 and MM721 BRI media modules to support both BRI trunks and BRI stations at the same time. However, MM720 and MM721 BRI media modules support combining both B-channels to form a 128-kbps channel. Communication Manager 3.1 supports combining B-channels using BONDing to form a high-bandwidth connection.

If you administer the MM720 or MM721 BRI media module to support BRI stations, you cannot use it as a clock synchronization source.