ADTRAN T1 ESF CSU ACE user manual Loopback Tests, Network Loopbacks

T1 ESF CSU ACE User Manual Chapter 1. Introduction

Loopback Tests

A number of different loopbacks can be invoked locally from the front panel, by T-Watch commands, or remotely by using special inband codes (AT&T network loop-up and loop-down codes). Additionally, the loopbacks can be remotely controlled by out-of-band commands using the T1 ESF FDL, or from T-Watch using a modem connection. A discussion of network loopbacks and DTE interface loopbacks follows.

Network Loopbacks

There are two types of network loopbacks: line loopbacks and payload loopbacks. These are illustrated in Figure 1-5.

•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 - Similar to line loopback, except that the framing is extracted from the received data and then regenerated for the transmitted data.

Figure 1-5. Network Loopback Tests

DTE Interface Loopbacks

Loops all data from the terminal interface (TI) back towards the T1. This loopback may be initiated using front panel, EIA-232 control port, or T-Watch commands. The DTE (or external test equipment) must provide any test pattern in order to check the DTE interface. See Figure 1-6.

Figure 1-6. DTE Interface Loopback

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