1. In
frequency-division multiplexing, a specific number of associated voice channels, either within a supergroup or as an independent entity.
Note 1: In
wideband systems, a group usually consists of 12 voice channels and occupies the frequency
band from 60 kHz to 108 kHz
. Note 2: this is
CCITT group B.
Note 3 : CCITT Basic Group A, for
carrier telephone systems, consists of 12 channels occupying upper sidebands in the 12-kHz to 60-kHz band. Basic Group A is no longer mentioned in CCITT Recommendations.
Note 4: A supergroup usually consists of 60 voice channels,
i.e., 5 groups of 12 voice channels each, occupying the frequency band from 312 kHz to 552 kHz. (
188 )
Note 5: A mastergroup consists of 10 supergroups or 600 voice channels. (
188 )
Note 6: The CCITT
standard mastergroup consists of 5 supergroups. The U.S. commercial carrier standard mastergroup consists of 10 supergroups.
Note 7: The terms "supermaster group" or "jumbo group" are sometimes used to refer to 6 mastergroups.
2. A
set of characters forming a unit for
transmission or cryptographic treatment. (
188 )