The L-ISDN channel unit has three LED indicators on the faceplate. A green ACTV LED indicates the plug-in card is busy. A steady red FAIL LED indicates that the plug-in card has failed, and a fl ashing red FAIL LED indicates illegal signaling. An amber LOOP LED indicates the plug-in card is in loopback.
Six (6) ISDN lines.
Each L-ISDN plug-in card accepts six ISDN lines. It uses 2B1Q (2 binary 1 quaternary) line coding for full-duplex transmission at 144-kbps data rate. The transmission format delivers 12 kbps for synchronization, 144 kbps for 2B+D customer data, and 4 kbps for DSL overhead functions. The customer data is divided into two 64-kbps channels (B channels) and one 16-kbps channel (D channel).