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4)
AUTO
POLARITY ON/OFF
[Logic operates
between
ground
(LOW)
and
+15V
(HIGH)].
IC26d and IC26c form
an
RS
flip-flop.
When
the
output
of
IC26c
is
HIGH,
it
prevents
lC14a and IC14b
(through
CR409)
from
changing
state,
thus
suppressing
the
Auto
Polarity function.
C218,
CR207
is
a
power-up
circuit for
IC14a,
IC14b
that assures
these
D
flip-flops
will
always power-up such
that the
polarity
is
non-inverted.
5)
Basic
Mode
Switching,
General
[This logic
operates
between -15V
(LOW)
and ground
(HIGH)].
Because
this
logic
can operate
in
either
Pulse
or
Continuous modes, and because
it
is
interconnected with
the
Recognition
circuitry,
it
is
substantially
more
complex
than the simple
logic
discussed above.
The Block
Diagram
in
Appendix E
shows
the
logic
(in
a
somewhat
conceptual
form),
and
should be used
in
conjunction with
this
description.
Briefly,
the
logic
uses
RS
flip-flops to
"remember"
the
Standby
state,
and
tri-state
gates
to electronically
switch
between
the output
of
the
RS
flip-flop
"memory"
and
the
User Control
Interface inputs
as required.
Auxiliary
circuits
determine
when
a
User
Control Interface
input
is
active
(a
normal
condition), or
when more
than one
such
input
is
active
(a
fault
condition
which
automatically invokes
Auto
mode).
An
Automation Lockout
circuit
enables
the
User Control
Interface
to
be
entirely
isolated
from
the
logic.
6)
Input
Decode And
Latches
lC39a,
IC39b
is
the
SYNTH
LEFT/RIGHT
latch
which
remembers
whether
LEFT
or
RIGHT
was
the
last
Synth
mode
invoked.
The
state
of
the latch
can
be
changed
by
the
Recognition
circuit
(through
CR301,
CR303),
by the pushbuttons (through
CR302,
CR304),
or
by the
User
Control Interface
(through
CR313, CR314;
and
through IC40a,
which
is
enabled
in
Pulse
mode
only).
IC39c,
IC39d
is
the
SYNTH/BYPASS
latch
which determines
if
the operating
mode
is
Bypass
or either
Synth
mode.
Its
state
can be changed
by the
same
sources
as
the
SYNTH
LEFT/RIGHT
latch.
In
addition,
CR306,
CR307
conduct
whenever
a
SYNTH
L
or
SYNTH R
input
is
received
from
any
source,
and
switch
the latch
into
Synth
mode.
IC27c, IC27d
is
the
AUTO
latch.
Its
state
can
be
changed
to
AUTO
by
means
of
the buttons, the
User Control
Interface (Pulse
mode
only),
and
the Fault output
line
through
CR309
from
the
User Control
Interface Status
Sensor
(see
below).
Its
state
will
be
changed
to
non-Auto
(through
CR310, CR311, CR312)
if
SYNTH
FROM
L,
SYNTH
FROM
R,
or
BYPASS
commands
are received
from
the buttons
or
User
Control
Interface.
Commands
from
the
Recognition
circuit
are specifically isolated
to
prevent
them from
turning
AUTO
mode
off.
When
the
yellow
STANDBY
lamps
are
enabled by the
User
Control
Interface
Active
sensor (IC32b) turning
Q311
on,
these
lamps always
indicate the status
of the input
latches.
The
outputs
of
the latches
are
decoded by
a
"tree"
arrangement
similar to
that
used
to
decode
the
WIDE/NARROW
lamps.
6-8
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