20. Delay lines are used in synchroscopes.
a. A synchroscope is an oscilloscope designed especially for the
observation of non-periodic pulses and transients. A synchroscope has all
the circuits of an oscilloscope plus two major additional circuits:
(1) A triggered horizontal sweep that sweeps the electron beam across
the scope only when a pulse is applied to the vertical deflection plates.
(2) A delay line that prevents the pulse from causing a vertical
deflection of the electron beam until shortly after the sweep has started.
The block diagram of Figure 39 shows how these circuits are used in a
Synchroscope Delay Line and Triggered Sweep.
b. The applied pulse triggers the sweep generator. The pulse applied
to the vertical amplifier input is amplified and fed to the sync pulse
amplifier, where it is amplified again and formed into a spike. The spike
triggers the sweep generator, which then sweeps the electron beam across the
face of the scope.
The sweep occurs when an incoming pulse triggers it.
Since the sweep starts at the same instant the pulse is applied, the leading
edge of the pulse may not appear on the face of the scope unless something
is done to prevent this possibility. That's the purpose of the delay line.