CHAPTER 6: Testing and Diagnostics
37
6.1.2 L
OCAL
L
OOPBACKS IN THE
R
EMOTE
M
UX
You can set two types of local loopback connections in the remote mux from a terminal hooked to the local
mux:
• T1 or E1 local, set for each T1 or E1 interface separately.
• Fiber optic link local.
The local loopbacks in the remote unit are activated by sending a special activation sequence through the link
when entering the appropriate command from the terminal.
Fiber optic link local loopback in the remote mux
When the fiber optic link local loopback is activated in the remote mux, the remote link interface returns the
transmit signal to the mux. Simultaneously, the remote unit sends an unformed all-ones signal to the link.
Figure 6-3 shows the fiber optic link remote loopback connection.
When the fiber optic link remote loopback is activated, the equipment connected to the remote unit channel
must receive its own transmission.
This test checks the operation of the remote unit and the connections to the equipment attached to the remote
channel interfaces.
Figure 6-3. Fiber optic link local loopback in the remote mux.
CAUTION
This loop connection irreversibly disconnects the link between the two muxes. To
reconnect the link, the user must shut down the remote unit and power it up again.
T1 or E1 local loopback in the remote mux
The T1 or E1 local loopback returns the T1 or E1 transmit signal to the output of the receive path. Figure 6-4
shows the T1 or E1 local loopback in the remote unit.
When the T1 or E1 remote loopback is activated, the equipment connected to the remote unit channel must
receive its own transmission. This test checks the operation of the connections to the equipment attached to
the remote channel interfaces.