There are oscilloscopes, function/signal generators, counter, and components tester in this category. Analogue oscilloscope is a traditional oscilloscope that is good for essential educating. The PC-based oscilloscope is working with the computer, it makes the display screen is unneeded. Now the digital technology makes storage and recall are possible for the digital oscilloscope. With the high sampling rate and memory depth, the bandwidth can reach 250MHz or even higher. And four channels oscilloscope can measure the four different signals at one time on one screen. Handhold oscilloscope or laptop oscilloscope always with the multimeter function. Now DDS function generator instead of the function generator with the advanced digital technology. More and more DDS function generator has two independent channels. The RF generator's frequency range can reach over 6GHz. Various counters with different functions and displays and the highest frequency can reach over 20GHz. Electron load is used for testing the DC power supply. Spectrum analyzer and distortion meter are used for testing the signal from the function generator. The component tester includes the transistor curve tracer and the LCR meter.