This device mixes the signals for terrestrial digital TV (Chideji), BS/CS, and CATV, and amplifies the terrestrial digital TV and BS/CS signals. It can also supply power to a BS antenna. I found this when I bought my house 10 years ago, but I never used it because the TV worked fine without it. I'm selling it now because I found it while cleaning. There are no instructions or original box. I'm not sure how to test it, so I haven't confirmed that it works. I'm selling it at a low price, but please understand that it is sold as-is (no returns/claims).