On edit:
I agree with KISS, it is a badly drawn circuit.
You have to know what the circuit looks like to understand the book which is trying to teach what the circuit looks like.
When I wrote my original reply, the thought did occur to me that the squiggle is often used to represent a break in a long line, but "prior knowledge" seduced me into ignoring that possibility here.
Some oscilloscopes use a long cable, effectively a transmission line, as the delay line.
JimB