Table of Contents
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Operation
of the
positive
trigger-recognition
circuit
is similar to that of the negative circuit.
D45 is the
recognition
diode,
and D55
is the
recovery
diode.
The
nega-
tive
trigger-recognition
circuit
is
locked
out by
-19
volts
through
POLARITY
switch
SW1OA,
and
R17.
The
holdoff
circuit
is driven when
D45
switches
to the high
state and sends a
signal to the base of QLO4.
D55 is switched to the low
state by the
collector
of Q84.
D45 and D55 are
connected
opposite
in polarity
to D25
and
D35.
Note
that
the
negative
trigger-recognition
circuit
actually
operates
on positive-
going
signals,
and
the
positive
trigger-recognition
circuit
operates
on negative-going
signals.
This
is because
trigger
signals
provided
to the
Type
5T1A
are
inverted
before
being
fed
to
the
trigger-recognition
circuits.
Operation
of the
trigger-recognition
circuits
in FREE
RUN is similar
to the operation
described previously.
The
input
is
driven
by
either
+19
volts,
in the
- POLARITY;
or
-19 volts
in the
+ POLARITY
position.
Holdoff
The
holdoff
circuit
prevents
the
trigger-recognition
circuit
from
operating
after
a trigger
has been
received
and
recognized
until
the
remainder
of the
system
is
ready
to
take
a new
sample.
The
holdoff
period
is
required
to allow
the fast ramp to run for a time equivalent to 10 em of dis-
play;
then
reset,
or to
limit
the
system
repetition
rate
to
100 ke,
whichever
time
is
longer.
The holdoff
period
is
- yarlable;
1.3:1
from
the
MAX.
to the MIN.
position
of the
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