 In modern digital systems, it is common for digital designs to be subject to analog effects, even if they operate at a relatively low clock frequency.Circuits operating at lower clock rates can behave as high speed digital systems if there is sufficient high frequency content in the signal edges (when transitioning between digital logic levels) relative to the distance traveled across a printed circuit board.As a result of improvements in semiconductor process, faster edge rates of even "low technology" electronic components can be sufficient to make the system effectively high speed and thus subject to havoc caused by unanticipated analog effects.