Complex sentence: In telecommunications, an extended superframe (ESF) is a T1 framing standard, sometimes called D5 framing because it was first used in the D5 channel bank, invented in the 1980s.
Split into simpler sentences: In telecommunications, extended superframe (ESF) is a T1 framing standard. ESF is sometimes called D5 Framing because it was first used in the D5 channel bank, invented in the 1980s.