Tait TB9100, Инструкция по установке и эксплуатации

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TB9100 Installation and Operation Manual Technical Description 97
© Tait Electronics Limited May 2006
Signal Paths
The digital board’s DSP and RISC, and the network board’s DSP and RISC
carry out signal processing and provide audio paths from the four external
inputs to the voter(s) and from the voter(s) to the four external outputs.
Figure 8.4 shows the main circuit blocks involved.
Speech signals received at the base station interfaces are either already in
packet form, or will be converted into packet form before reaching the
voter. The packets have a different format depending on the base station’s
mode. When the base station is in digital P25 mode, speech is encoded as
IMBE packets. When the base station is in analog FM mode, speech is
encoded according to the G.711 standard.
The voter selects the winning speech packets and routes them according to
the destination ID stored in their header data.
Input Signal Paths
The following section describes the signal processing that takes place on the
signal path between each reciter interface and the voter.
From the RF
interface (Digital
P25)
Figure 8.5 shows the signal path from the RF interface to the voter(s) for a
digital P25 call.
Figure 8.4 Reciter block diagram
Packet
Switch
ADC ADC
ADC
Voter
P25
Modem
Mod/
Demod
IMBE
Enc/Dec
G.711
Enc/Dec
FM Audio
Process
RTP
RF
Interface
Control Panel
Speaker/Microphone
Digital
Network
Analog Line
IMBE G.711
IMBE
IMBE/G.711 IMBE/G.711
Digital
Board DSP
Network
Board RISC
Network
Board DSP
IMBE
Dec*
Buffer Buffer