ADTRAN TSU 600 user manual Tsu, Network Loopback Tests

Chapter 1. Introduction

Classes of Loopbacks

There are two classes of loopbacks: network interface and DTE interface.

Network Interface Loopbacks

Network interface loopbacks (see Figure 1-9) affect the entire T1 data stream. There are two types of network loopbacks, line loopback and payload loopback.

Line loopback loops all of the received data back toward the network. The transmitted data is the identical line code that was received, including any bipolar violations or framing errors.

Payload loopback is similar to line loopback, except that the framing is extracted from the received data and then regenerated for the transmitted data.

TSU 600

NI CSU

DS1

Payload Loopback

Line Loopback

Secondary

Interface

Figure 1-9

Network Loopback Tests

DTE Interface Loopbacks

DTE interface loopbacks affect only that portion of the data stream programmed to that particular interface port. The Nx56/64 serial interface offers two loop- backs, a DTE loopback and a port loopback. See Figures 1-10 and 1-11.

DTE loopback loops all data from the DTE back towards the DTE. This loopback occurs just past the interface circuit allowing a verification of the opera- tion of the DTE to TSU 600. This loopback may be initiated by using front panel or T-Watch commands. The DTE (or external test equipment) must provide any test pattern in order to check the DTE interface. See Figure 1-10.

18 TSU 600 User Manual 61200.076L2-1