The interior of this AC 220v Wireless Wifi Smart Power Wall Socket Electrical Wifi Smart Plug Outlet is very clean. It actually marks the VCC, RX, TX and GND connections, so it is easy to solder the header to it and replace the firmware. It can accommodate all high voltage circuits such as switching relays and current monitoring circuits. It contains all the digital components. It has a black plastic sheet at the top center that prevents light from different status LEDs from flowing into the wrong part of the display. AC 220v Wireless Wifi Smart Power Wall Socket Electrical Wifi Smart Plug Outlet also has a sticker with the part number printed on it. AC 220v Wireless Wifi Smart Power Wall Socket Electrical Wifi Smart Plug Outlet has a varistor and a resettable fuse for protection. It also has a small transformer with a diode and a small amount of capacitance to reduce the voltage to power digital components. The plug itself is overmolded or pressed into a plastic housing and soldered directly to the PCB.