To this point the presentation has discussed the basics of an oscilloscope. It will now focus on how to get the signal of interest to the oscilloscope. The discussion will be about different probing techniques, including passive probes, which are typically standard with most modern oscilloscopes. Passive probes vary in bandwidth from 350-500 MHz and in some of the lower end products 100 MHz passive probes are available. Active probes will also be discussed in depth. These are typically higher in bandwidth, much greater than 500 MHz and require power because they are transistor based. There are also differential probes which require the user to use one channel as opposed to using two single ended probes and then doing the math, subtracting one from the other. High voltage probes are useful when debugging and troubleshooting high voltage power supplies, for example. Finally, there is a wide variety of current probes for measuring current.