Daniels P25, Руководство пользователя

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UG-001 Daniels P25 Radio Systems
www.danelec.com
Chapter 4: P25 System Block Diagrams 21
User
Guide
B A S E S TAT I O N B L O C K D I A G R A M
Figure 4-2 shows a block diagram of a Daniels P25 analog controlled base station system. The receiver
will receive the incoming FM or C4FM transmission and will automatically detect and demodulate the
signal to an analog or P25 digital signal. The signal is then converted into a digitally sampled signal
and then routed through the analog or P25 digital settings programmed into the receiver. Analog signal
settings may include CTCSS or DCS decoding, de-emphasis and wide or narrowband selection. P25
digital settings will include NAC and/or TGID decoding. The digitally sampled signal is then routed out
of the receiver as analog audio out the subrack / motherboard to the base controller. If a P25 digital
signal is sent out as analog audio, the signal must fi rst be de-vocoded before it can be converted to
analog audio. MT-4D Base receivers may have an optional AES or DES-OFB decryptor module.
The analog audio is then routed through the base controller (CI-BC-4E Base Controller) and is sent
to the auxiliary audio output for connection to an external device such as a tone remote adapter. The
auxiliary audio input from the external device is routed through the base controller and is sent to the
transmitter. Internal audio levels between the receiver, base controller and transmitter are typically set
at -8.0 dBm for 60% of maximum modulation. Independent audio level controls in the base controller
allow the auxiliary input and output levels to be adjusted separately (default is 0 dBm for 60% maximum
modulation). An optically isolated PTT input is routed through the base controller to the transmitter for
keying.
The transmitter will accept the incoming analog audio and route it through the analog or P25 digital
settings programmed into the transmitter. Analog signal settings may include CTCSS or DCS encoding,
pre-emphasis and wide or narrowband selection. P25 digital settings will include NAC, TGID and
Unit/Source ID encoding. MT-4D Base transmitters may have an optional AES or DES-OFB encryptor
module. The transmitter will then modulate the analog or P25 digital signal as either FM or C4FM,
based on the analog or digital software settings, or the front panel switch.
Figure 4-2: P25 Base Station Block Diagram
BASE OR REPEATER
RECEIVER
BASE OR REPEATER
TRANSMITTER
BASE
CONTROLLER
RF IN RF OUT
A / D
DETECT
A D
CTCSS / DCS
DECODE
DE-EMPHASIS
FILTER
NAC / TGID
DECODE
DE-VOCODER
A / D
SELECT
A D
CTCSS / DCS
ENCODE
PRE-EMPHASIS
FILTER
NAC/TGID/SID
ENCODE
VOCODER
BALANCED
AUDIO
INPUT
FM ANALOG OR
C4FM DIGITAL
FM ANALOG OR
C4FM DIGITAL
1 KHz TONE
@ -8.0 dBm
= 60% MAX. MOD.
AUXILIARY
BALANCED
INPUT
BALANCED
AUDIO
OUTPUT
1 KHz TONE
@ 60% MAX MOD
= -8.0 dBm
AUDIO
OUTPUT
(TO SYSTEM
MONITOR SPEAKER)
OPTIONAL
DECRYPTION
AUXILIARY
BALANCED
OUTPUT
AUDIO
LEVEL
CONTROLS
1 KHz TONE
@ 60% MAX MOD
= 0 dBm
COR
1 KHz TONE
@ 0 dBm
= 60% MAX MOD
OPTIONAL
ENCRYPTION
AUXILIARY
PTT
OPTICAL
ISOLATOR
PTT
INPUT