Wikipedia
Digroup
Digroup is an abbreviation for digital group. In telephony, a basic digital multiplexing group.
In the North American and Japanese T-carrier digital hierarchies, each digroup supports 12 PCM voice channels or their equivalent in other services. The DS1 line rate (2 digroups plus overhead bits) is 1.544 Mbit/s, supporting 24 voice channels or their equivalent in other services.
In the E-carrier European hierarchy, each digroup supports 15 PCM channels or their equivalent in other services. The DS1 line rate (2 digroups plus overhead bits) is 2.048 Mbit/s, supporting 30 voice channels or their equivalent in other services.