Tait TB9100, Installation And Operation Manual

Page: 103 / 144

TB9100 Installation and Operation Manual Technical Description 103
© Tait Electronics Limited May 2006
To the Transmitter
(Analog FM)
Figure 8.10 shows the signal path from the voter to the RF interface for an
analog FM call.
The winning signal is processed as follows.
1. The voter passes the signal to the G.711 encoder/decoder, which
decodes the G.711 packets and passes them to the packet switch.
2. The packet switch switches the signals to the audio circuitry for
analog FM calls, which encodes any subaudible signaling (e.g. DCS,
CTCSS).
3. The Modulator/Demodulator circuitry converts the audio frequency
to the required RF frequency (VHF or UHF).
4. The ADC turns the sampled bitstream into the analog signal that is
sent to the exciter.
To the Analog Line
The signal processing on the audio path from the voter to the analog line
(not illustrated) is as follows:
1. The voter switches the winning packets to the appropriate decoder
(IMBE encoder for digital P25 packets or the G.711 encoder for ana-
log FM packets).
2. The packet switch routes the resultant digital voice stream to the
ADC for the analog line.
3. The ADC converts the digital voice stream to analog audio, which is
put on the analog line.
Figure 8.10 Path from voter to transmitter (analog FM mode)
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