CHAPTER 2: Introduction
11
2.3.4 T
EST AND
D
IAGNOSTIC
C
APABILITIES
Each mux comes with comprehensive test and diagnostics capabilities, including local loopback on the fiber
link interface and remote loopbacks on each channel link. The remote loopbacks are activated on the remote
units. To perform activation, send a special test sequence through the fiber link. An automatic self-test on
power-up further enhances maintenance. For activation of the above and other loopbacks, see Chapter 6.
Alarms and alarm indications
The muxes can detect the following alarm conditions on each T1 or E1 and fiber interface:
• Loss of input signal.
• Loss of frame synchronization.
• Reception of alarm indication (AIS) signal, which consists of a continuous sequence of ones (“1”s).
NOTE
When AIS is received, loss of frame synchronization occurs. However, in this case, the
alarm indicating loss of frame synchronization is suppressed.
If the user isn’t using all of the channels, the user can disable the alarm indications related to the unused
channels. The response to alarm conditions is as follows:
• The detection of loss of fiber input signal, the reception of AIS on the fiber input, or loss of fiber frame
synchronization result in the transmission of AIS on each channel output.
• For each channel, an AIS signal is sent instead of the channel data stream through the fiber link upon
detection of loss of channel input signal, the reception of AIS on the channel input, or loss of channel
frame synchronization.
Front-panel indicators display each alarm condition. The mux also uses a dedicated connector to provide major
and minor alarm indications by means of dry contacts. The major alarm is activated in the following cases:
• The mux isn’t powered or there’s a total power-supply failure on either the primary or backup power
supply.
• There’s a loss of fiber optic input signals or loss of fiber optic frame synchronization.
• There’s a loss of channel input signals or loss of frame synchronization.
The minor alarm is activated in the following cases:
• There’s reception of AIS signal on the fiber optic input.
• There’s reception of AIS signal on channel inputs.