Features: This musical coil features wireless transmission and a speaker for tubes and bubble It is the perfect teaching tool to stimulate students interest in science and makes a great gift. For wireless transmission experiments, It can be used to create high voltage lightnings and perform various scientific experiments such as wireless transmission, wireless lighting and insulator withstand voltage testing. Teachers use it to demonstrate to students the principlesof enhancement and high frequency skin effects, etc. This musical coil has a circuit-protected design that will not damage the input device. Wireless connection for cell phones is convenient. Specifications: Music Format: Only Squarewave Music Can Be Played Input: WirelessConnection With Cell Phone Length: About 30-70mm / 1.2-2.8" (Actually May Be Shorter Or Longer) Power: 0-100W Temperature Control Function Material: Metal Size: About 13x8x8cm/5.12x3.15x3.15in Package Includes: 1PC Music Coil note: Because the frequency is too high, the heat of the MOSFET will be relatively large. Please pay attention to the temperature of the heat sink when using, so as to avoid high temperature (mainly music modes) damage components. During use, please do not place explosives items within 5m/16.4ft. Due to the serious interference with the metal. Please do not approach the coils of electronic devices such as cell phones and computers to avoid damage. Because the diameter of the secondary coil is very small, try not to bumpto avoid damage to the secondary coil winding Please do not modify the equipment without permission to avoid accidents. Do not use illegally. For viewing only, if you do not know usage, please do not open it yourself.