Chapter 7. Test Menu61202129L1-1 TSU 120 User Manual 7-3Network TestsNetwork tests control the activation of loopbacks and the initia-tion of data test patterns.Network tests are run on the Network Interface (NI). You canselect three different test configurations to determine the typeof loopback and the pattern to run. Test results display in theLCD window.Executing NETWORK TESTS will disrupt normal data flowunless only TST DS0S are selected for testing.Loopback TestsA number of different loopbacks can be invoked locally fromthe front panel, by T-Watch commands, or remotely by usingspecial in-band codes (AT&T D4 network loop-up and loop-down codes). Additionally, the loopbacks can be remotely con-trolled by means of out-of-band commands by the T1 ESF FDLor from T-WATCH Pro by a modem connection.Network Interface LoopbacksNetwork interface loopbacks (see Figure 7-2 on page 7-4) affectthe entire T1 data stream. There are two types of network loop-backs, LINE LOOPBACK and PAYLOAD LOOPBACK.Line LoopbackLine loopback loops all of the received data back toward thenetwork. The transmitted data is the identical line code thatwas received, including any bipolar violations or framingerrors.Payload LoopbackPayload loopback is similar to line loopback, except that theframing is extracted from the received data and then regener-ated for the transmitted data.
