The peak pulse current ratings are measured using laboratory generated pulses that are designed to simulate the pulses caused on cables by nearby lightning strikes. These waveforms are called double exponential waveforms. The 8 by 20 waveform is used to specify the peak pulse current in the AK because it is the standard pulse wave form used to rate the peak pulse current of metal oxide varistor products, also known as M-O-Veez. Since the AK series is designed as a premium play in the MOV space, using the same rating system makes it easy for the design engineer to select the appropriate AK series for the application. 8 by 20 means that the current wave will take eight microseconds to achieve its peak value and will take twenty microseconds to decay to half of the peak value. Specifying three things, the peak value, the rise time and decay time fully define the waveform. Smaller TVS diodes are rated using a much, much longer 10 by 1000 waveform which is commonly used in telephone circuits. The 8 by 20 waveform is defined in the IEC 61000-4-5 test specification. This is the global specification for devices placed on AC power lines and is recognized around the world. What is key to understand here is that the peak pulse current rating for AK devices are much, much higher than the peak pulse current ratings for smaller TVS devices for two reasons. One is that the AK series devices contain a lot more silicon and metal than a standard TVS device and are much more robust. The second reason is that the AK series is rated using a much shorter current pulse, so the peak pulse current rating will be much higher.