Instruction manual

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The other non-adaptive mode provides the user with access to all the link
bandwidth that is not used by the voice channel. In this mode, the data
channel can serve data terminal equipment capable of operation in accord-
ance with the rate of the clock signals provided by the DV-MUX3, includ-
ing operation at data rates which are not necessarily based on the
n × 75 bps scheme.
Thus, the DV-MUX3 allows using a single modem link for the transmission of two
voice/fax channels, and in addition allows the transmission of a data channel.
The DV-MUX3, especially when operating in its unique adaptive multiplexing
mode,offers veryhigh bandwidth efficiency without introducing the long, variable
link delay typical of statistical multiplexers.
Voice/Fax Channel
Features
The DV-MUX3 can be ordered with one or two voice/fax channels. To reduce band-
width requirements yet achieve high quality voice transmission, the voice channels
process the audio signals using a standard digitizing algorithm (MPMLQ - Multipulse
Maximum Likelihood Quantization per ITU-T Rec. G.723), and adaptive echo can-
cellation.
The bandwidth assigned for the transmission of a voice channel is user-selectable:
4.8, 6.4, 7.2, 9.6 or 12.8 kbps. This bandwidth includes in-band signaling and syn-
chronization overhead. When operating at a digitized voice data rate of 6.4,7.2, 9.6
or 12.8 kbps, the end-to-end voice performance is nearly toll quality. To improve
the perceived link quality, the DV-MUX3 voice channel includes an adaptive echo
canceler that handles near-end reflections (echo delay less than 8 milliseconds)
such as reflections caused by the hybrids used for 2W/4W conversion. The echo
canceler convergence time is better than ITU-T Rec. G.165 requirements.
To maintain voice quality on bad communication links, when operating at 7.2, 9.6 or
12.8 kbps the DV-MUX3 voice channels include Hamming forward error correction
(FEC) coding that protects the critical information bits in the digitized voice data
stream. The FEC code can maintain voice quality for link error rates down to 1×10
-3
.
Each channel supports fax transmission for Group 3 fax machines in accordance
with ITU-T Rec. T.4 and T.30 at rates of 2.4, 4.8, 7.2 or 9.6 kbps (according to
voice channel rate). Each channel automatically identifies the type of signal (voice
or fax) and switches accordingly between the voice and fax modes. Therefore, the
user can follow the regular fax operating procedures.
Each voice channel has its own level adjustment switches, to provide optimal se-
lection of receive and transmit levels.
The voice channels are available in three options:
• 2W FXO interface: two-wire 600-ohm analog interface and FXO loop-start
signaling for direct connection to PABX extension lines.
• 2W FXS interface: two-wire 600-ohm analog interface and FXS loop start
signaling for direct connection of a subscriber telephone set. The FXS inter-
face generates locally the required line feed current and the ringing voltage.
• 2W/4W E&M interface: two-wire or four-wire analog interface and E&M
signaling. This interface supports five types of E&M signaling: RS-464
types I, II, III and V, and British Telecom SSDC5 (except the signaling bat-
tery voltage is -24V, instead of -48V).
CHAPTER 1 - INTRODUCTION
1-2 DV-MUX3 Installation and Operation Manual