Kenwood TR-2600A - Page 4

TR-2600A/E
CIRCUIT DESCRIPTION
@ Control circuit
1) Squelch system
To minimize battery drain, the squelch switch is closed
during reception (When the DCS switch is on}, and power
to the AF output IC and S meter amplifiers is shut off
during transmission. In the K,X, & M models the AF IC
remains on during tone pad operation to permit monitoring
keypad tones.
The logic state of each section in each mode is given below.
© During transmission R5 goes tow, and T5 goes high.
C___svta Te Te
Psooren | t pw [a [a |
Psociose fH [et [ey
mani D
DCS ON :
Wp ae
Seer ya
*: Varies according to are =
squelch switch is open or closed.
14PIN SQ OPEN/ GROUNDED
SQ CLOSE/ OPEN
©
During
reception
Because
of
T5,
Q18
turns
on
so
that
both
A
and
B
go
low.
©
(K,M,X
models
only)
when
the
OTMF
pad
is
keyed,
F
goes
high
and
O79
turns
on,
so
that
D
goes
low
and
A
and
B
go
high.
Fig.
3
Control
circuit
(squelch)
RX
unit
2) Standby system
© During reception mode
D14
conducts,
so
that
voltage
is
applied
to
Q23,
which
turns
on.
this
turns
on
Q22
so
that
B
+
voltage
is
developed
during
reception.
Q26
is
always
on
if
the
TXS
terminal
is
low.
However,
since
Q28
is
off
during
reception,
no
current
flows
from
Q26
emitter
to
collector.
This
results
in
both
Q25
and
Q24
remiaining
off.
© During transmission mode
S8
(PTT)
is
closed.
When
Q27
and
O28
turn
on,
current
flows
from
Q26
emitter
to
collector.
Q25
and
Q24
turn
on,
2nd.
T5.B+
voltage
is
developed
during
the
transmission
mode.
At
this
point,
since
the
TC
line
is
low,
D15
conducts
with
the
result
that
O23
and
O22
turn
off.
© Manual TX stop
Because
the
TC
lines
can
be
open
by
S1,
the
transceiver
cannot
enter
transmission
mode
when
the
PTT
switch
is
depressed.
Oo TXS terminal
While
the
transmission
out-of-band
inhibit
is
on,
digital
codes
are
being
indicated
or
while
the
call
sign
is
being
indicated,
a
logic
high
signal
is
sent
from
the
micro-
processor
to
the
TXS
terminal,
and
Q26
turns
off.
At
the
same
time,
the
level
at
the
base
of
G23
goes
high
through
R6O
and
R57
and
the
transceiver
cannot
enter
transmission
mode.
© During digital code transmission
A
logic
high
signal
is
fed
to
the
ATX
and
ME
terminals
from
the
microprocessor
with
the
result
that
Q34
turns
on.
This
mutes
the
audio
input
from
the
microphone,
and
at
the
same
time,
the
unit
enters
transmission
mode.
©
During
touch
tone
transmission
(K,M,
& X
models
only)
If
the
keypad
is
operated
during
transmission
DOTMF,
mod-
ulation
is
available.
At
this
time,
Q33
pin
10
goes
high,
and
this
is
fed
to
Q34
via
D29
and
030.
This
allows
Q34
to
turn’
on,
which
mutes
the
microphone
input.
At
the
same
time,
since
once
DTMF
keypad
operation
begins,
C86
charges
and
the
transmission
mode
is
held
for
approx.
2
seconds.