RS-170 was the original black-and-white television signal standard defined by the EIA (Electronics Industries Association). The RS-170 video standard specifies the timing and signal characteristic of broadcast video in the United States, Japan, and several other markets. It specifies a composite signal with well-defined voltage, sync levels and blanking timings, at a horizontal refresh rate of 15.75-KHz and a 60-Hz vertical interlaced scan frequency. RS-170 delivers 625 lines of resolution, with the odd and even lines interlaced at 60 half-frames per second (30 Frames per second). The 60-Hz field rate was chosen to give adequate full-motion-video capability while avoiding interference from ac current fields.