This device transmits radio waves carrying time information for radio-controlled clocks in indoor environments where it is difficult to receive the standard radio waves for radio-controlled clocks. The dedicated app can be opened via the QR code on the back of the main unit. I've used it for about 5 years, and it has been working without any problems. Everything is shown in the photos, but the instruction manual can also be downloaded from the manufacturer's website. According to the manufacturer's website: This is a radio clock transmitter that maintains the time based on the AC signal obtained from a household AC100V power supply. It operates by adjusting the internal clock's lag and advance, focusing on the fact that the AC100V power frequency (50Hz/60Hz) is controlled to prevent cumulative errors. If you set the time initially using a web browser application, the internal clock will be maintained by adjusting the time using the AC signal thereafter. The transmission distance to the radio-controlled clock is up to 10m.