multiplex hierarchy
In frequency-division multiplexing, the rank of frequency bands occupied:
12 channels
group
5 groups (60 channels)
super group
5 super groups (300 channels)
master group (CCITT–now, ITU-T)
10 super groups (600 channels)
master group (U. S. standard)
6 U. S. master groups (3600 channels)
jumbo group