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APPENDIX B
CELP VOICE CHANNEL MODULE APPLICATIONS
OVERVIEW
The CELP Voice Channel Module reduces the effective data bandwidth
required by a speech circuit passing through the TMS-3000/TMS Compact,
Univ. MM+ V4 or MINIMUX TDM network. Three bit rates are offered
under software control: 4.8, 6.4 or 9.6 kHz. The speech compression
function will be performed using digital signal processing techniques. It
takes a standard E&M speech channel and, through speech reduction
algorithms, defines parameters of the speech. These parameters are then
transmitted at a lower bit rate to the receiving end where they are
reconstituted back into speech again.
The CELP Voice Channel Module provides good business communica-
Quality Telephone
tions quality voice channels at 4.8, 6.4 kHz or 9.6 KHz. Customers
Voice
typically find the voice quality at these rates to be more than acceptable
for their purposes. An all-digital "echo canceller" conforming to CCITT
recommendation G.165 has been included on the CELP Voice
Channel
Module. This
eliminates
the
need
for
cumbersome
external
echo
cancellation equipment in most applications.
This voice channel is designed for conveying speech. Other audio forms
FAX Bypass Option
(e.g., music), may not be transmitted. Modems will not transmit data
since phase information contained in the carrier will be lost.
One main application of the CELP Voice Channel Module is to maximize
voice channel capacity of n x 64 kHz aggregates on TMS-3000/TMS
Compact, Univ. MM+ V4 and MINIMUX TDM networks. This is
especially important on long haul routes where bandwidth costs remain
high.
As shown in Figures B-1 and B-2, two PBXs communicate via their ana-
log tie lines through a user's private TMS-3000/TMS Compact, Univ.
MM+ V4 or MINIMUX TDM network, respectively. Analog voice is
compressed into digital data in the CELP Voice Channel Module and
transmitted via data links to a remote CELP Voice Channel Module. This
reduces many of the noise and quality signal problems associated with
analog tail circuits in public telephone networks. Existing voice lines
can thus be eliminated or a new voice network added with no increase in
line cost. In the U.S. or Canada, simply connect the CELP Voice Channel
Module between a TMS-3000/TMS Compact, Univ. MM+ V4 or MINIMUX
TDM and a spare port of your telephone system and you have a private
voice circuit. There is no costly upgrading of existing equipment, no
increase in line costs and minimum installation/maintenance costs.
B-1
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