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Issue 01 - 06/99 4 - 5
Testing in Simulate Mode - Section 1
About Voice Calls
Voice calls are a useful way of testing audio quality on
the line. For example, you could make a voice call to
another engineer or to a recorded service and listen to
received voice signals.
Although you can have voice calls in progress on all B
channels simultaneously, the Codec (audio coder/
decoder) can only be connected to one B channel at a
time. In other words, you can only listen to the channel
that is currently displayed on the screen.
In Basic Rate, the second call remains connected, but
without the Codec. This means you can switch between
the two channels and listen into each call.
If a data call is in progress, you can make or receive a
voice call at the same time. This is a useful test to detect
any cross-channel interference which may be present.
Notes for DASS users
Three types of Speech Call are available— 3.1K AUDIO ,
SPEECH C1 and SPEECH C2 . Category 1 calls require,
and are guaranteed, a fully digital path while Category 2
calls may be routed over analogue lines at some point
during the call. Therefore, Category 1 speech calls are
only accepted by ISDN telephones, whereas Category 2
may be used to call analogue or ISDN telephones. For
further information, refer to BT specification BTNR190
Vol. 1 Sections 0-8.
About Data Calls
Data calls can be used to test the quality and integrity of
the line. This is done by running a Bit Error Rate (BER)
test in the data connection established by a call. For
information on BER testing, refer to Section 2 of this
Chapter.
Chap4s1.PM6 17/06/99, 09:41 5