AVT MAGIC ISDN, Hardware Description

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PA G E 2 9
S Y S T E M D E S C R I P T I O N
2.7 The ‘ Audio Layer II/III Analog I’ Board
This Analogue board provides the user with earth-free and symmetrical in-
puts/outputs for the Audio signals. Additional possibilities are setting levels,
selecting impedance, multiplexing various Audio signals and level monitoring.
The possibility exists via jumpers, for mid-point earthing of the Audio signals
at the main audio interface. The jumpers are marked on the printed circuit
board. As delivered, the mid-point earthing is not jumpered (see
SECTION 3.7).
FIGURE 2.9 shows the main components of the Analogue board. The control
of the Analogue card is from the Codec unit over the so-called Host-Bus. MUX
and DEMUX are arranged via an Audio crossbar, through which the different
Audio signals can be switched.
FIGURE 2.9 BLOCK DIAGRAM OF AUDIO LAYER II/III ANALOG I BOARD
Level control from Codec Host
Main In
Analog
Command channel from IFE
AUX In
Mux/Demux control from Codec Host
to Codec Host
to Encoder DSP
Deemphase control from Codec Host
from Dec.
DSP
Main Out
Analog
Level control from Codec Host
to Codec Host
Command channel to IFE
AUX Out
Level control
-12 dBr
M
U
X
D
E
M
U
X
A
D
A
A
A
D
Level control
-12 dBr