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2
S Y S T E M D E S C R I P T I O N
The block diagram of the system is shown in Fig. 2.
FIG. 2
RS232C
TTL USER I/O
HSD (Relay)
LSD (Keypad)
AES/EBU
Analogue
2.1
Functionality
Via the Telephone Hybrid system three or four callers pre selected can go On
Air simultaneously. Additionally there is a call forwarding function to fixed
numbers. The signal receivedby the caller can either be from the analogue au-
dio interface or from the handset. The caller's signal is always available at the
handset or and simultaneously at the audio-interface.
For each of the maximum of four callers, a digital Echo Canceller is available.
This Echo Canceller is necessary to suppress disturbing echo when normal
analogue telephones are used by the caller.
Likewise, the Automatic Gain Control (AGC) can be turned on for each caller.
To suppress disturbing noise of callers who are currently not speaking, the
Expander can be activated.
In the conference mode there is the possibility of mixing all callers digitally
and connecting the mixed signal to one interface. The callers get the digitally
generated Mix Minus signal.
Three relays (HSD interface) are available for external signalling. The follow-
ing conditions can be displayed:
– at least one caller is ON AIR
– at least one caller is in PRE TALK
THE BLOCK DIAGRAM OF THE MAGIC ISDN TELEPHONE HYBRID
basic-construction
AES/EBU
Line 1
ANALOGUE
Line 2
Module
Line 1
Line 2
(Optional)
Audio codec
- Analogue Audio
- G.711 Codec
S y s t e m
D e s c r i p t i o n
Line-
interfaces
2 x S
0
ISDN Module
DSP
- Echo Canceller
- N-1, AGC
Standard
- Digital mixing
Audio-
interfaces
Handset
Audio (CMD)
P A GE 1 7
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