The SP achieved improvements over the original format by using a higher-energy tape and extending the FM carrier. There were very different versions for 525-line and 625-line picture formats. Unlike S-VHS, the deviation of the FM carrier was kept the same in both the SP and regular versions so that older machines could play the newer tapes. That was true even in 625-line formats, but an older, "low-band" U-matic was incompatible with both "high-band" and SP.