Editing U interface (section)

===TCM / AMI===
The TCM / AMI ISDN line system, also referred to as TCM-ISDN, is used by [[Nippon Telegraph and Telephone]] in its "INS-Net 64" service.<ref name="inoue-tcm-isdn">{{cite journal |title=Implementation in Japan (ISDN) |journal=IEEE Communications Magazine |volume=30 |issue=8 |pages=54–57 |doi=10.1109/35.149619 |date=August 1992 |publisher=IEEE |last=Inoue |first=O.}}</ref>

Appendix III of G.961 specifies a line system based on the [[#Time Compression Multiplex (TCM)|Time Compression Multiplex]] (TCM) duplex method and an [[alternate mark inversion]] (AMI) line code.<ref name="G.961"/> The AMI line code maps one input bit to one ternary symbol.<ref name="G.961"/> Like with MMS43, the ternary symbol can either be a positive (+), zero (0), or negative (-) voltage.<ref name="G.961"/> A 0 bit is represented by a zero voltage, while a 1 bit is alternatingly represented by a positive and a negative voltage, resulting in a DC-bias free signal.<ref name="G.961"/> In a 2.5&nbsp;ms interval, each side can send a 1.178&nbsp;ms frame representing 360&nbsp;bits of 2B+D data.<ref name="G.961"/> To the 2B+D data, an 8-bit preamble, 8 bits from the C<sub>L</sub> channel, as well as a parity bit are added, yielding a frame size of 377&nbsp;bits and a baud rate of 320&nbsp;kilobaud.<ref name="G.961"/> The C<sub>L</sub> channel is used for operations and maintenance, as well transmitting a 12-bit CRC covering 4 frames.<ref name="G.961"/>