INSTALLATION AND MAINTENANCE MANUAL
E1 FAMILY
LICENSED & SPREAD SPECTRUM RADIOS
JUNE 2001
SECTION 2: PRODUCT DESCRIPTION
PAGE 2-17
2.3.4
Controls
Loopback is a test method used which transmits either an internal or external
E1 test signal and loops this E1 signal back at the far-end radio (re-transmits
the signal back to the near end). The near end then receives the signal. This
is very useful for testing because the test signal can be monitored at the
near-end and the quality of the entire link can be measured using a Bit Error
Rate (BER) test, or internal test features, without anyone going to the far-end
radio location.
ERROR
When lit RED, this indicates that a bit error occurred while in loopback mode. If you
are not using a BER test set, this LED may be observed to determine if there are any
bit errors during loopback, for example during an overnight test.
ENABLE
This is a push-button switch that executes the loopback mode for the corresponding
channel. Loopback is initiated by pressing and holding this switch for approximately 3
seconds. Once in loopback mode, the LED which is embedded in the switch is
illuminated YELLOW to indicate that Loopback is ON. The LED on the near-end radio
flashes while the far-end is solid. Loopback is disabled by pushing and releasing the
ENABLE button at either the near-end or far-end radio.
Enabling loopback will interrupt traffic. This is an out-of-service test.
CH SEL
This is a push-button switch provided only on the 4xE1 and 8xE1 versions that selects
the channel for loopback mode. The channel is determined by the number of times the
switch is pressed. Press (hold for 2 seconds and release) for channel 1, press again
for channel 2, and press again for channel 3 and press again for channel 4. In the
case of 8xE1, select channel the same way but look for channel indication on the
seven-segment LED read out. On the 4xE1 radio, loopback is initiated using the
ENABLE switch; the LED in the CH SEL button flashes in a group sequence to
identify which channel is selected for loopback. On the 8xE1 radio, loopback is
selected the same way but indicated on the 7-segment LED read out.
DISPLAY
FAR END
This push-button provides the capability to determine alarms and status of the far-end
radio. When pressed and held, the alarm and status LEDs and the RSL test point
correspond to the far-end radio’s status and RSL value. This can be used for
installation, maintenance and troubleshooting. When the LED on this switch is
flashing, no far-end information is available. This typically indicates that there is no
link between near-end and far-end radios.
