D4

Also known as M24 Superframe, with M meaning Multiplex. A T-carrier framing convention that enables bit robbing of the least significant bit (LSB) of the sixth and twelfth frames, only, of a 12-frame sequence or superframe.Voice and data both are accommodated, with data treated as a digital input. Ones density must be maintained through the insertion of stuff bits. See also bit robbing, D1, D2, D3, ESF, frame, LSB, ones density, superframe, and T-carrier.