Answer :

Delay line is used to delay the signal for some time in the vertical section. The Figure below (which figure?) indicates the amplitude of signal wrt (avoid short-forms) time and relative position of the sweep generator output signal. The diagram shows that when the delay line is not used, the initial part of the signal is lost and only part of the signal is displayed. To counteract this disadvantage this signal is not applied directly to the vertical plates but is passed through a delay line circuit. This gives time for the sweep to start at the horizontal at the horizontal plates before the signal has reached the vertical plates. The trigger pulse is picked off at a time t0  after the signal has passed through the main amplifier .

The sweep generator delivers the sweep to the horizontal amplifier and the sweep starts at the HDP at time t0 + 80 ns. Hence the sweep starts well in time, since the signal arrives at the VDP at time t0 + 200ns.Delay line is used to delay the signal for some time in the vertical section. The Figure below (which figure?) indicates the amplitude of signal wrt (avoid short-forms) time and relative position of the sweep generator output signal. The diagram shows that when the delay line is not used, the initial part of the signal is lost and only part of the signal is displayed. To counteract this disadvantage this signal is not applied directly to the vertical plates but is passed through a delay line circuit. This gives time for the sweep to start at the horizontal at the horizontal plates before the signal has reached the vertical plates. The trigger pulse is picked off at a time t0  after the signal has passed through the main amplifier .The sweep generator delivers the sweep to the horizontal amplifier and the sweep starts at the HDP at time t0 + 80 ns. Hence the sweep starts well in time, since the signal arrives at the VDP at time t0 + 200ns.