A good answer might be:

ON.. the analog signal (continuously changing voltage signal) moved up and down, but at time "T" it is clear that it is above the threshold. Exact measurement is not needed.

Analog signals, such as the one above, continuously change in value. But by agreeing on a threshold, binary data ("on" / "off" ) data can be represented. It is easy and fast (for electronics, as well as humans) to tell if something is above a threshold or below the threshold.

Here is the voltage signal we might send down our wire to transmit the data "off" followed by "on". (The wire is examined at times t1 and t2.)

QUESTION 6:

Is is clear that the signal is "off" at time t1 and "on" at time t2?