Specifications

12
of DB-15 connector, respectively. In this case, the external signals are referenced
to ground and may be a.c. or d.c. coupled depending on the user requirement.
Especially, if the type of external modem is AFSK or FFSK, Sub-audio
Squelch(SQ) System can be applied by dealer programming. For reference, its
related parameter is “Tx Tone Generation for Data Input” of “Tx option” group
on the “System Option / GPS” tap window of ACC-916.
Brief block signal flow diagrams for each input are the following (See Figure 2.1. ~ 2.3.).
Audio signal flow in Transmitter
Pre-emphasis
Audio Amp. & Filter
Level
Detector
300Hz HPF
Analog S/W
MC14053B
Data BPF
Sub-Audio LPF
MF6
Z1
Z
Y1
Y
Adj. Level
MCU
Check Audio In
Tone En
Audio In
Mod Out
Sub-Audio
Encoder
Y0
Z0
X1
X
X0
High : Audio In
Low : No Audio
300Hz HPF
Analog S/W
MC14053B
Sub-Audio LPF
MF6
Z1
Z
Y1
Y
MCU
Audio Mute
Y0
Z0
X1
X
X0
Pre-Selector
RF Board
Sub-Audio LPF
4th Order
AF
IF IC
TA31136FN
RSSI
Audio Amp.
Comparator
MF6
Audio Mute
Tone Detector
RSSI
Audio Out
LM386
Busy
Audio signal flow in Receiver
Figure 3.1. Audio signal flow diagram
Level
Detector
Data BPF
MCU
Check Audio In
Data Enable
Audio In
Mod Out
Data In
High : Audio In
Low : No Audio
If audio input is absent,
Data path will be enabled.
In this case,
Sub-audio option is ignored.
Data signal flow in Transmitter
RF Board
AF
IF IC
TA31136FN
RSSI
Data
Out
BPF
30Hz ~ 5KHz
MCU
RSSI
Busy
Comparator
Data signal flow in Receiver