User Manual

INSTALLATION AND MAINTENANCE MANUAL
LYNX.sc E1 FAMILY
SPREAD SPECTRUM RADIOS
OCTOBER 1998
PAGE 3-30 SECTION 3: INSTALLATION & ADJUSTMENTS
3.12.5 AIS Enable/Disable
AIS (Alarm Indication Signal) is the blue code (all 1’s) that keeps the digital line interface active
under data loss conditions. AIS is required by certain equipment to maintain synchronization (for
example, it is required on all leased line circuits). However, it is not required by all equipment (for
example, a CSU/DSU will initiate its own blue code to the line under data loss conditions).
Under test conditions, when measuring receive threshold, for example, it may be necessary, to
disable AIS to facilitate BER measurement.
There is a user selectable DIP switch segment on the rear panel of the LYNX.sc radio that
includes selection of the AIS function (on/off) at the receiver line output. When the AIS is selected
(on), the CEPT-1 signal will send blue code to the line when the received BER exceeds 1 x 10
-3
.
This function is similar to a data “mute” function. When the AIS is disabled (off), no insertion of
data will take place unless an RX SYNC alarm condition occurs. Refer to Figure 3-15 for DIP
switch segment information.
The standard factory setting is to have the demodulator AIS alarm selected ON because it
prevents a severely errored signal (possibly unsynchronized) from being sent out to the line.
It is recommended that AIS be selected ON for normal operation.
It is recommended that AIS be selected OFF for measuring BER
at threshold.
This DIP switch does not affect AIS injection into the
transmitted data stream upon a DATA LOSS condition.
Figure 3-15: AIS Switch