TM-V71A/V71E
9
6-3. Microphone Key Input
■
When the MC-59 (Supplied microphone) is used
The pulse is output from the CM terminal of the MPU to
the microphone. The MPU judges which key was pressed
from the number of pulses returned from the microphone.
■
When the MC-45 (Optional microphone) is used
The microphone UP/DOWN and function keys are
connected to the microprocessor analog input. The voltage
when a key is ON operates the corresponding function.
100K
22K
22K
100K
PTT
UP
DOWN
CALL
VFO
MR
PF
R985
R984
R983
CP952
5M
MIC PTT
MIC UP
MIC DW
MPU
IC918
MIC
Fig. 12 Microphone (MC-45) key input
7. Data Terminal and Peripheral Circuits
J607 (Data terminal) is the data communications terminal
on the rear of the transceiver. It handles transmission
control, data input/ output, and squelch signals.
There are two data communications modes: 9600bps
mode and 1200bps mode. 9600bps mode communications
are GMSK and G3RUH packet communications. Unlike with
1200bps AFSK, with this type of high-speed modulation,
frequency modulation is carried out after the digital base
band signals (rectangular wave) are passed through a band
limiting filter. For 9600bps GMSK for example, compared
to 4800Hz signals (nearly sine wave signals passed
through a fi lter), the signals have a hissing sound like digital
modulation when listened to by ear. Different types of
modulation, such as GMSK and G3RUH, are distinguished
by the type of band limiting fi lter used.
Pin No. Pin name
Specifi cation
1
PKD
bps switching
1200bps
9600bps
Modulation input
40mVp-p
2Vp-p
Frequency shift
3±0.5kHz
2.2±0.5kHz
4
PR9
Output level 500mVp-p/10k
Ω
Always output during reception
5
PR1
Output level 500mVp-p/10k
Ω
Not output when squelch off
Table 2 DATA terminal input/ output level
7-1. Transmission Signals
Transmission modulation signals enter from PKD of the
data terminals (J607). The path to the modulation depends
on whether communications are set for 1200bps or 9600bps
mode.
For 1200bps mode, the transmission modulation signals
pass through the analog switch (IC803), and are input to
IC801 (Pin 6). The signals pass through the pre-emphasis
(Q801, Q802), are adjusted by the electronic volume, and
are input to the VCO.
For 9600bps mode, the transmission modulation signals
pass through IC803 and are amplified by the tone amp
(IC802). Signals are then adjusted by the electronic volume,
and are input to the VCO.
The frequency shift depends on the input signal level, so
there is an amplitude limiting circuit (D702, D703) to hold
the signal below 4 Vp-p to avoid extreme shifts. This circuit
ensures that the PKD signal does not go above 4 Vp-p and
there is no extreme frequency shift fl uctuation.
Fig. 13 Transmission signals
Q807
Q606
Q816
Q804
Q803
Q805
Q808
Q811
IC805
1/2
IC805
1/2
DE-EMPHASIS B
Q607
Q806
Q810
DE-EMPHASIS A
IC918
MPU
CTCSS Filter AMP
BEEP
DTMF
MUTE1
MUTE2
IC806
Cross
Point
SW
IC804
E VR
IC804
E VR
IC804
E VR
ATT
IC801
AF AMP
J801
(SP1)
J802
(SP2)
IC666
Multi
SW
IC486
FM IC (A)
IC546
FM IC (B)
IC806
Cross
Point SW
IC805
1/2
IC803
1/2
IC803
2/2
D607
D609
Limiter
1200bps
9600bps
PRE-EMPHASIS
MOD AMP
VCO
TCXO
IC807
PR9
SQC
PKS
PKD
PR1
CIRCUIT DESCRIPTION