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The areas to be considered for a design engineer to successfully suppress EMI on the PCB are firstly, issues arriving from fast rise and fall times in system clocks. Secondly, issues from VCC transients during semiconductor "wake up" and thirdly, common and differential mode noise on VCC and GND lines. For EMI filtering and shielding, the inductive filtering blocks or reflects selected frequencies, thus leaving that energy within the circuit. The capacitive filtering de-couples selected frequency to GND or a ground plane. Metal cans and shielding block contains HF noise, again retaining it within the system. Ferrite filtering absorbs HF noise and converts that HF noise into small amounts of heat, thus removing it from the system completely.