Signal edge

Image:Digital Signal Square Wave.svg|thumb|Signal edges of a periodic digital signal indicated in blue
In electronics, a signal edge is a transition of a digital signal from low to high or from high to low:

A rising edge is the low-to-high transition.
A falling edge is the high-to-low transition.

In the case of a pulse, which consists of two edges:

The leading edge is the first edge of the pulse.
The trailing edge is the second edge of the pulse.