AVT MAGIC AC1 XIP/XIP RM, Hardware & Software Manual

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PAGE 67
W i n d o w s P C S o f t w a r e
– Telephone : Normal telephone connection with 3,1-kHz band width in
transmit and receive transmission.
– J.52 : IUT-T Standard, which allows a so-called Capability Exchange
1
and a permanent delay compensation
2
when 2 B channels are used. De-
pending on the implementation, transparent data channels can be also
transmitted. An unsymmetrical Audio transmission (e.g. MPEG with 2
B in transmit direction, 7-kHz in receive direction) is also possible. This
procedure is supported by several manufacturers (e.g. MAYAH Cen-
tauri). For
MAGIC DC7/AC1 this procedure is set by default.
– OFF : No signalling is used. The encoded Audio data is transmitted wi-
thout any further framing. With this way of signalling only one B chan-
nel can be used. The procedure is possible with almost every Audio co-
dec on the market.
If
G.722 (7-kHz) is selected as Audio quality (see below), the so-called
SRT procedure ( Statistical Recovered Timing ) is used when no signal-
ling is selected.
– MusicTaxi : This proprietary signalling is used by Audio codecs from
the company Orban (former Dialog4) and has been also implemented
by some other manufacturers for compatibility reasons. 2 B channels
can be transmitted. The Audio transmission is symmetrical, i.e. the
same coding algorithm must be used in transmit and receive direction.
– CCS-L2 : A further proprietary signalling from the company Musicam
USA (in Europa formerly CCS). The procedure supports only a symme-
trical Audio transmission with ISO/MPEG Layer II with up to 2 B
channels. Therefore, the fee-based option
ISO/MPEG Layer II Upgrade
(order number 450305) is required to use this signalling.
• Under Audio Quality TX you select the Audio quality for the transmit di-
rection. Depending on the selected Transmission Type the following set-
tings are available:
– G.722 (7-kHz)
– MPEG (15-kHz)
• The Audio quality in receive direction ( Audio Quality RX ) can only be sel-
ected for the transmission type J.52 , since all other procedures only allow
a symmetrical Audio transmission. The following options are available
3
:
– G.722 (7-kHz)
– MPEG (15-kHz)
• The setting Bit Inversion allows an inversion of the encoded Audio signal
and is only available when OFF is selected as signalling type.
1
Capability Exchange: At the beginning of the connection, the systems exchange information
about how many B channels are possible, which Audio coding algorithms and specific codec pa-
rameters are available etc. After this exchange, the best possible transmission mode is set auto-
matically. However, you have also the possibility to force a certain procedure, e.g. when you only
need a 7-kHz connection.
2
B channels are routed separately in the ISDN network. When Audio signals are transmitted with
128-kbit/s, the two B channels have to be set together at the same time at the receiver which is
done by delay compensation. This procedure is called Inverse Multiplexing. If B channels are re-
routed in the network because of line errors during the connection, an Audio transmission with
a static delay compensation, which was measured at the beginning of the connection, would not
work any longer. J.52 adapts the delay compensation dynamically and is protected from delay
variations.
NOTE
If you defined only a 1B connection for Connection 1 , you can define addi-
tionally a Telephone or 7-kHz (Auto) connection for the second B channel.
So you can establish connections with two different algorithms to two diffe-
rent partners at the same time.