Instruction manual

4-2. DESCRIPTION OF DIAGNOSTIC FUNCTIONS
General A test or loop is activated on the channel selected by the SELECT switch by de-
pressing the corresponding DV-MUX3 front-panel push-button. As long as any
test or loop is activated, the TEST indicator lights.
To deactivate the test or loop, press the same push-button again. If this was the only
active test or loop, the TEST indicator will turn off.
The commands for the activation/deactivation of remote loops is transmitted end-to-
end through the main link. Therefore, when a remote loop is activated, the DV-MUX3
TEST indicators light at both ends of the link.
BERT Test The BERT test is available only on the data channel. This test is used to obtain a rapid
qualitative evaluation of data transmission without using external test equipment.
When the test is activated, a test signal is applied to the selected channel of the DV-
MUX3. The test signal, an internally-generated 2
9
- 1 (511) bit pseudo-random se-
quence, is internally connected to the input of the tested channel transmit path. The
transmitted data can either be returned to the receive path of the channel by means
of a loop somewhere along the data path (e.g., by connecting the remote channel
loop, or by a physical loopback connection), or a similar sequence can be transmit-
ted from the other end of the data channel (either by simultaneously activating the
BERT test at the remote DV-MUX3 or by connecting a test pattern generator).
The received signal is routed to an internal test sequence evaluator. The evaluator
compares the received data, bit by bit, to the original data and detects any differ-
ence (bit error). Each detected error is indicated by flashing the RD/ERR indicator.
While the BERT test is activated, the CD and CTS lines in the local data channel
connector are set low (inactive).
Tone Injection The test tone (1000 Hz, 0 dBm) is a digital sequence repeating at a rate of 1000 Hz
generated by the digital voice processor and sent to the remote side. The sequence
is identical to the data stream that would have been generated if a 1000 Hz signal
at a nominal level of 0 dBm were applied to the input of the voice channel being
tested. Therefore, the remote user can hear the tone in the telephone earpiece, and
can also make measurements using test equipment.
When the DV-MUX3 is equipped with a voice module with two channels, the tone
is simultaneously sent on both channels.
Since the tone is sent in only one direction (toward the remote DV-MUX3), the
other direction operates as usual.
The tone canceler suppresses the tone on the receive side of the local voice channel,
therefore any attempt to activate tone injection at both ends of the link, or to use a
remote loopback while the tone is sent, will not allow you to hear the tone.
CHAPTER 4 - DIAGNOSTICS
4-2 DV-MUX3 Installation and Operation Manual