This very compact and useful device can be obtained from eBay, AliExpress or other similar services already for ~10 dollars + shipping. The price is really peanuts and absolutely worthwhile for anyone wanting to do any kind of homebrew electronics. Just connect a 9V battery, insert an electronics component into the slots, press the button and ta-daaaa-m: the specifications of the component are displayed on the LCD screen almost immediately. Different types of transistors, MOSFETs. diodes, thyristors, resistors, capacitors, and other components can be tested with ease. Awesome!