The collector output of Q5, as shown in Fig-
ure 15,
is
coupled to the junction of resistors
R33 and R61. Resistor R33, diode D31, capac-
itor C3, resistors R61 and R62, and capac-
itor C60 form filters. These filters direct
voltage from Q5 to clamp Q3 and Q6 to make
the dashes self-completing. They also keep the
control voltage from interacting between dots
and dashes.
The output from the collector of Q5
is
also
coupled through a delay line consisting of re-
sistors R70, R71, R72, and capacitors C70 and
C71 to the base of Q7. This delay
is
necessary
to insure that the output switching caused by
the flip-flop multivibr ator slightly overlaps
that of the dot generator, while making dashes.
Failure to overlap may leave holes in the
dashes similar to that caused by the bouncing
contacts of relays.
When the collector output of Q5 remains at its
maximum negative voltage level,
it
produces
a
negative voltage to turn on transistors Q7 which
drives Q8. Before Q5 can switch to on, the flip-
flop must be triggered again by a positive going
pulse from the collector of Q2. The pulse that
just triggered Q5 was apositive goingpulse from
Q2. The output from the dot generator multi-
vibrator
is
now a negative voltage from the col-
lector of Q1. This
is
fed tothe base of 47, which
is
already on because of the negative voltage
at Q5. Therefore, the output from Q1 has no
additional effect. The next pulse from Q2 will
be
a negative going pulse, as Q2 turns off.
This negative pulse from Q2 has no effect on
the flip-flop multivibrator, as only positive
going pulses can reset it. After the dot gen-
erator multivibrator goes through another half
cycle, a positive going pulse from Q2 will
result. This positive pulse
is
coupled to the
base of Q4 (saturated transistor), resetting
the flip-flop multivibrator.
Note in Figure 14 that the flat portion of the
waveform
is
equal to the length of a dot and a
space. This
is
because Q2 produces &positive
going pulse every time it switches on. Since the
positive pulses switch the flip-flop transistors
alternately, they operate at half the rate of the
dot generator multivibrator. The output from the
dot generator and flip-flop multivibrators addat
Page
39
A FOR
REFERENCE
ONLY
TO
T1
T2 T3 T4
TIME
COLLECTOR VOLTAGE
Figure
15
the base of Q7. This produces the first third
of a dash signal from the collectors of
Q1
and
Q5, as shown in Figure
15.
The middle third of
the dash
is
produced by the collector output of
Q5 alone.
TO
TI T2
T3
T4
TlME
Q1
COLLECTOR VOLTAGE
Figure
16
The last third of the dash
is
filledin by the next
dot signal from Q1 alone as shown in Figure 16.
The result of these two signals at the base of
Q8
is
the waveform shown in Figure 17,
TO
TI
T2 T3 T4
TlME
SIGNAL AT BASE OF
Q8
Figure
17
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