TM-V71A/V71E
8
5-3. Serial Control
The MPU (IC918) controls the panel section (Display unit
X54-359) through synchronous serial communications.
PANEL
X54-359
MPU
IC918
Fig. 9 Structure of non-synchronized serial
communication
5-4. Narrow/ Wide Switching Circuit
On band A, the receiver bandwidth can be switched
between narrow and wide by selecting IF ceramic filters
CF487 (Narrow) and CF486 (Wide) with a switching circuit
(Q486, Q487, D486, D487).
On band B, the receiver bandwidth can also be switched
between narrow and wide by selecting IF ceramic filter
CF547 (Narrow) and CF546 (Wide) with a switching circuit
(Q546, Q548, D546, D547).
The transmitter deviation can be switched between
narrow and wide by setting the electronic variable resistor
(IC804) on the deviation adjustment point. It is controlled
from the MPU (IC918).
CF486
IC486
FM IC
D486
D487
CF WIDE
CF487
CF NARROW
CF546
IC546
FM IC
D546
D547
CF WIDE
CF547
CF NARROW
Fig. 10 Narrow/ Wide switching circuit
6. AF Signal System
6-1. Beep Circuit and Mute Circuit
A beep sound is generated by the MPU (IC918) and goes
to cross point switch (IC806). This signal is switched by
the cross point switch and is input to the electronic volume
(IC804). While the beep signal is output from the MPU,
audio signals for each band are muted by the cross point
switch with the serial data from the MPU (IC918). The beep
signal that has had its level adjusted by an electronic volume
is input to AF amplifi er (IC801).
6-2. Speaker Switching Circuit
There are two speaker jacks, J801 (SP1) and J802 (SP2).
The AF signals can be output in various combinations
matching the internal speakers. When an external speaker is
not connected to J802 (SP2), the J802 signal is added to the
AF amplifi er input of SP1 via the ATT circuit, and is output
through J801 (SP1). When an external speaker is connected
to J802 (SP2), it is output separately from a speaker for A /
B band. Crossing point switch connection can be switched
by switching the menu between MODE 1 and 2, and the
connection of SP1 and SP2.
The AF signal output combinations are shown in the
table below.
Mode
Speaker
Setup
Band Output
Internal
Speaker
External
SP1
External
SP2
MODE 1
None
A, B
–
–
SP1 only
x
A, B
–
SP2 only
A
–
B
SP1, SP2
x
A
B
MODE 2
None
A, B
–
–
SP1 only
x
A, B
–
SP2 only
B
–
A
SP1, SP2
x
B
A
Table 1 AF signal output combinations
Q807
Q811
IC805
1/2
IC805
1/2
DE-EMPHASIS B
Q806
Q804
Q803
Q810
DE-EMPHASIS A
IC918
MPU
CTCSS Filter AMP
BEEP
DTMF
IC806
Cross
Point
SW
IC804
E VR
MUTE1
MUTE2
ATT
IC801
AF AMP
J801
(SP1)
J802
(SP2)
IC666
Multi
SW
IC486
FM IC (A)
IC546
FM IC (B)
Q816
Fig. 11 Beep circuit and mute circuit
CIRCUIT DESCRIPTION