The Datavideo VP-634 3G/HD/SD-SDI Repeater is a non-powered complement to the optional VP-633. Both extend an SDI video signal along with embedded audio 328 ft. Both re-clock to maintain signal quality. And both support resolutions up to 1080p/60 NTSC or 1080p/50 PAL, automatically detecting whether the input is NTSC or PAL. The 633, however, is DC-powered and meant only to serve as the initial extension unit, the first link in the extension chain. The 634 only joins at the end of the first 328 ft and thereafter every 328 ft. The initial unit -- the 633 -- will feed power to as many 634 units as you connect.