An ISDN configuration where several T1 facilities can be controlled by a single D-channel, instead of the normal T1 configuration where each T1 facility has 23 B-channels and a D-channel (23B+D). With NFAS, all 24 timeslots of the nonsignaling trunks are available for voice whereas only 23 channels can be used on the trunk that carries signalling traffic (23B+D+n24B). See also D-channel backup.