DS0 Testing
The DS0 test feature enables testing on each of the 24 channels of the T1 line. The receive
channel is decoded and the VF level and frequency are measured and displayed. The signal
is also connected to a speaker, enabling the tester to make an audible assessment of the sig
-
nal quality of the circuit. If the circuit is out of service, the tester can insert a test tone on
the transmit channel for measurement at a remote location with another test set, or locally
with a loopback.
Configuration
Before conducting channel tests, the T1 interface must be properly configured. From the
Setup menu, select the correct Framing Mode, Line Coding and Clock Source. If the testing
is in-service, the
Receive Input must be configured for either Bridged or Monitor modes. The
receive mode should be set up before connecting to the circuit to avoid creating a "hit" on
the customer data. If the testing is in-service, the Site Master transmit pair should not be
connected to the circuit.
If the measurement is out-of-service, the
Receive Input mode should be Terminate, and the
Site Master transmitter can be connected to the circuit. The current configuration of the T1
interface is displayed in the status window at the bottom of the screen.
Channel Tests
Once the unit is correctly configured, press the VF Channel Access soft key and select the
DS0 menu to perform tests at the channel level. Press the Select Channel soft key to select
specific channels. Either enter a specific channel number from the keypad, or scroll through
the channels with the Up/Down arrow keys. The received VF level and frequency on the se-
lected channel are displayed, and the decoded signal is connected to a speaker for audio
monitoring. When a test tone is present on the channel, the level and frequency report will
indicate whether the channel is healthy. If speech is present on the channel, the channel per-
formance can be judged from the audio quality. A picture of channel utilization can also be
formed by quickly scrolling through the channels.
If the circuit is out-of-service, the user can also connect to the transmit pair and insert a test
tone on the selected channel (note that transmit and receive must be on the same channel).
Two menus enable selection of transmit level and frequency. The frequency can be entered
from the keypad, or scrolled to common test frequencies (404 Hz, 1004 Hz, 1804 Hz, 2713
Hz, and 2804 Hz) with the Up/Down arrow keys. To check the performance of channel
level equipment, the test tone can be measured at a remote location with another VF chan
-
nel test set, or locally with a loopback. To establish a loopback, use the loopback menus in
the BERT test suite.
9-12
Chapter 9 T1 Measurements
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