(i) Multivibrator (V8). When triggered by a positive pulse,
the multivibrator will produce a rectangular wave whose leading edge
A coincides with the transmitter pulse. The trailing edge B will
coincide with the trailing edge of the transmitter pulse.
(j) Clipper (V9). To ensure that the positive pulses do not
interfere with the multivibrator circuit operation, they are removed
by a clipper circuit.
(k) Multivibrator (V10). When triggered by a negative pulse,
the multivibrator produces a rectangular waveform whose leading edge
coincides with the trailing edge of the transmitter pulse. This
rectangular waveform, to be used as the receiver gate, has been
delayed by a time equal to the width of the transmitted pulse.
(1) Multivibrator (V12A and V12B). A single multivibrator
stage consists of two tubes. When the multivibrator is triggered by
a positive pulse, each tube will develop a rectangular waveform. The
waveforms will be 180 out of phase with each other. The two
rectangular waveforms are used as the indicator and marker gates.
(3) Timer requirements. To provide the required timing pulses,
a timer must include a circuit capable of establishing the pulse
repetition frequency, a means of forming the desired signals with the
proper time relationship, and circuits designed to protect one
component from the loading effect of another and to deliver pulses to
the loads without distortion. The same signals can be made with use
of solid state circuits as seen in Figure 12a.
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