G.707中关于N1字节各BIT的定义
Bits 1-4 are used as an Incoming Error Count (IEC); the coding is given in Table D.2.
Bit 5 operates as the TC-REI of the Tandem Connection to indicate errored blocks caused within the Tandem Connection.
Bit 6 operates as the OEI to indicate errored blocks of the egressing VC-n.
Bits 7-8 operate in a 76 multiframe as:
–the access point identifier of the Tandem Connection (TC-APId); it complies with the generic 16-byte string format given in 9.2.2.2.
-the TC-RDI, indicating to the far end that defects have been detected within the Tandem Connection at the near end Tandem Connection sink.
-the ODI, indicating to the far end that AU/TU-AIS has been inserted into the egressing AU-n/TU-n at the TC-sink due to defects before or within the Tandem Connection.
-reserved capacity (for future standardization).
