Chapter 1. Introduction61200060L1-1 TSU User Manual 1-13DTE Interface LoopbacksThe Nx56k/64k serial interface offers a DTE loopback. SeeFigure 1-8.DTE Loopback: loops all data from the DTE back towardsthe DTE. This loopback may be initiated by the DTE assertingthe Local Loopback (LL) input on the connector or by usingfront panel or T-WATCH commands. The DTE (or externaltest equipment) must provide any test pattern in order tocheck the DTE interface.Figure 1-8. DTE Interface LoopbackPattern GenerationThe TSU offers four available test patterns, All Ones, 3:24,and 511 and 1:8.All OnesNeed definition3 in 24The 3:24 is a stress pattern which places the maximumnumber of 0s in the transmitted data. This is always doneover all DS0s. This pattern is used in conjunction withexternal test equipment to determine if the T1 line ispreforming acceptably under a stress condition.TSUto DTET1DTELoopbackNx56/64InterfaceNx56/64 tonetwork controlcircuitNetwork Interface(NI)
