Philips PM 3266 - Page 103

108
In
the
composite
triggering
mode,
which is
only
functional
when
also
ALT mode
is
selected,
point 4
of
S22-A
is open
circuited,
consequently,
transistors
V408
and V458
and
also
transistors
V457
and
V407
are now
controlled
by
a signal
coming from
the vertical
logic
circuit
via
R1622
and V462.
This
signal
brings
transistors
V458
and V408
alternately
into
conduction
to enable
triggering
on
the
channel
being
displayed.
Transistor
V459
inverts
the
logic
input
signal
to
allow
alternate
switching
of the
two
channels.
Diodes
V454
and
V404
are
alternately
conducting
and
the
A and B
trigger
signals
are
alternately
routed
to
the
MTB trigger
amplifier.
Presets
R426
and
R476
enable
the switching
points
of the
diodes V404
and V454
to be
set.
Presets
R472
and R422
compensate
for
any
current
differences
between
the
A and
B
triggering
signals
to
enable
the
same
current
to be delivered
to the trigger
amplifiers.
3.2. 7.5.
Vertical
display
mode logic
y-DEFLECTION
SELECTION
SIGNALS
CON'BOL
AlT
PULSE
SIGNAL
FROM
MAIN
FOR
COM-
TiME-SASE
POSITE
TRIGGERING
Fig.
3.5.
Vertical
display
mode logic
MAT
93
This
logic consists
of digital
circuits employing
dual-in-line
TTL integrated
circuits. Vertical
mode
selection is
made
by selector
switch
SI.
The
outputs that
can be selected
by the vertical display
mode selector switch
SI
are:
—
channel A only
—
channel B only
—
TRIG VIEW
signal
only
—
channels A and
B added,
chopped or alternated
—
TRIG VIEW
signal
and channels A
and B, chopped or alternated.
Positive logic
is used in
the digital
circuits, the levels being
as
follows:
logic
"1"
=
-t5
V (high)
logic
"0"
=
0
V
(low)
The different
functions
of the logic
circuits are now described
according
to
the vertical display
mode
selector
switch
SI
.
A
—
selects channel A
only. Via switch
SI
the S input
(point
7)
of
flip-flop
D1604
is
set to
t-5
V
and the R input (point
8)
to
0 V. The
"high"
level at output 10
is fed via two NOR
circuits and R1628 and R1626 to R289
in the A channel
preamplifier
to open
the
A channel signal path.
At
the same time the
control signals for the
B and the
TRIG
VIEW channel
are
0
V.
B
—
selects channel A
only. Via switch
SI
the
S input (point
7)
of flip-flop D1604
is set
to 0 V and the R input (point
8)
to
-1-5
V. The high
level
at output 1 1 is
fed via
two NOR circuits
and
R1627
and R1624
to R389 in the B channel
preamplifier
to open the B channel
signal path.
At the
same time the control
signals for the
A
and the
TRIG VIEW channel
are
0
V.