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).
The L-ISDN plug-in card provides the interface towards the switch, including the DC termination of the sealing current. The L-ISDN card supports three (3) DS0 TDM and has built-in BER measurement.