Payload
Loopback
Line
Loopback
Figure 4-2 E1 Loopback Block Diagram
MAC
Media Access
Controller
DTE
Processor
Figure 4-3 DTE Loopback Block Diagram
4.3.1.1 Line Loopback and DTE Loopback
Line loopback is illustrated in Figure 4-1. The incoming DS1 line signal is looped back to the outgoing DS1
signal before the DS1 transceiver framer. This loopback is used to isolate the local equipment from a
troubled DS1 transmission line. Line loopback test can be activated from the terminal.
4.3.1.2 Payload Loopback
Payload loopback is illustrated in Figure 4-1. The incoming signal is loopback to the outgoing DS1 signal
after the DS1 transceiver framer. This loopback is used to isolate the DTE port from the troubled DS1
transmission line. Payload loopback test can be activated from the terminal.
4.3.2 Far End Loopbacks
Far-end loopbacks (remote line loopback, remote payload loopback) can be activated by the local ip6610 to
cause a remote facility to perform the loopbacks. Inband codes, AT&T and ANSI FDL protocols, and
proprietary codes are utilized to send remoter loopback commands to the far-end facility. Inband code
words are supported by D4, ESF, or ESF&DS1.403 framing format. When using AT&T FDL messages, the
Line port must be set for ESF or ESF&DS1.403 framing format. When using ANSI FDL messages, the Line
port must be in ESF&DS1.403 framing format. All remote loopback can be activated from the terminal.
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