Lumped parameter delay lines consist of number of cascaded symmetrical LC network called T-section. Each section is capable of delaying the signal by 3-6 nsec. Such filter is shown in the figure (a) .It acts as low pass filter with cut off frequency as,

$f_{c}= \dfrac{1}{\ \pi{}\ \sqrt{LC}}$

If the input voltage consists of frequency much less than cut off frequency, output signal will be faithful reproduction of input voltage but delayed by the time,

$f_{c}= \dfrac{1}{\ \pi{}\ {f_c}} = \sqrt{Lc}$

Where   ts = delay for single T-network

While  td = n ts

Where  td = total delay

n = number of T-section

A practical delay line circuit in CRO is driven by push pull amplifier and is shown in above figure.