109
ADD
TRIG
VIEW
CHOP
ALT
TRIG
ALT VIEW
I I
TRIG
VIEW CHOP
I
I
—
adds
channels
A
and
B.
Inputs
2 and
5
of NOR
circuits
D1603
are
connected
to
+5
V
via
switch
SI
,
consequently
both
outputs
1
and
4 are
low. They
are
fed
via
the
NOR
circuit
and
the
resistors
to
R289
and R389
in
the A
and B
channel
preamplifiers
to
open
both signal
paths
simultaneously.
The
TRIG
VIEW
control
signal
is
0 V then.
—
selects the
trigger
signal
only. Via
switch
SI a
+5
V is applied
to points
4 and
5
of NAND
D1607
(4-5-6).
Output
point
6 is fed via
NOR D1602
(1-2-3)
and
resistors
R1
629 and R
1 623 to R547
in
the trigger
view
amplifier
to open
the
trigger
view
signal
path.
The
channel A
and B
control signals
are 0 V then.
—
selects
channels
A and B
chopped. In
this position
the
chopper
generator,
which consists
of NAND
circuits D1601
(4-5-6)
and D1601
(1-2-3), is switched
into
the circuit
by a
-)-5
V applied
to
input
4. The
frequency of
oscillation is
2 MHz. The output
signal
is fed via
two NANDS to the
clock input of
flip-flop
D1
604.
The
only flip-flop
of
interest now
is the first
one. It divides
the
incoming frequency
by two
and
switches
at
a
frequence of
1 MHz.
The
resulting
high
switching levels
on the
outputs 10 and
1 1 of the flip-flop
provide the
chopping
signals for
the A and B channels.
The
control signal
for
the TRIG VIEW
channel is blocked
in this situation.
During switching over
in the CHOP mode,
the c.r.t.
is
blanked
by pulses
supplied
via transistor
VI 601 to R2002 of
the blanking
stage.
—
selects
channels A and B
alternately for display. The
circuit acts as in the
CHOP
mode, only the chopper
generator
is
blocked
and the circuit
is
driven
now
by
the
much slower switching signal
applied
to input 2 of NAND D 1 608
(1-2-3).
This
switching signal
is derived from the main time-base generator (V903)
or
the alternate time-base
logic. These pulses switch
the circuit
at
the
end
of
each
sweep
and the channels A and B are
alternately displayed.
In
ALT TB mode
the circuit
is
switched
at
the
end of every two sweeps.
The control signal for
the TRIG
VIEW
channel is
0
V.
—
selects channels A and B
and
TRIG VIEW
alternately.
So three signals can
be
made
visible
on the screen,
but
only
one at a time is written.
For
the generation of
the
control
signals see Fig.
3.6.
Clock
pulses are here the
alternate pulses.
—
selects channels A
and B and
TRIG VIEW
chopped.
Three signals can be made
visible
on the screen,
but
now in chopped mode.
For
the generation of the
control
signals
see
Fig. 3.6. Clock pulses are here the
chopper generator
output pulses.
Composite
triggering
The output
signal of point
10
of
flip-flop D1604
is
applied via R1622
to
diode V462
in the trigger source
selector.
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