NCP>LOOP LINE DUP-0

          This command initiates a line-level loopback test over
          X25 line DUP-0.  The software loops one message, 4096 bytes
          in length, with mixed binary information.

      NCP>LOOP LINE DUP-1 COUNT 10 WITH ONES

          This command initiates a line-level loopback test over
          X25 line DUP-1.  The software loops 10 messages, 4096 bytes
          in length, with all binary ones information.