Automatic TX/Rx switch and On/Off switch. (1)To reach the Max output, the input power also should be the MAX.(2)The input power should be within the range, or it will be damaged. (3)The different modes work under different conditions, so please check instruction before using it. Though the working frequency range is HF (330MHz), the MOST effective range is suggested between 20 and 30 MHz(15,12,10 meter). Please check your usual using range to arrive the best frequency before placing orders. The amplifier should be used with DIRECTOR CURRENT (Operating voltage 13.8Vcc), so it will need some professional tools to help the amplifier work if only with household alternating current. Whats more, the antenna will directly affect the input and output signal, and the antenna frequency is 3-30MHz, so please check its frequency to suit the amplifier. International Buyers - Please Note. Please send us message before your return the item, we will offer you the right return address. However, don't disassemble the product by yourself. If have any problems, please send us message first. Our goal is to make sure you are a happy customer and pleasant shopping with us. Please give us the opportunity to resolve any problem , We understand the concerns and frustration you might have , and will try our best to resolve the issues. Please do not leave any negative or neutral feedback before send us message. We try our best to deliver great service to our customers, to satisfy you in every aspect. The item "HYS SSB AM FM CW high power HF 3-30MHz Power Amplifier+FAN for portable radio" is in sale since Friday, September 1, 2017. This item is in the category "Consumer Electronics\Radio Communication\Ham, Amateur Radio\Ham Radio Amplifiers". The seller is "189shop" and is located in Quanzhou,Fujian. This item can be shipped to North, South, or Latin America, all countries in Europe, all countries in continental Asia, Australia.