Frequency modulation (FM modulation). U-matic saw two revisions to improve its image quality. The first was high-band or Hi-band, introduced for PAL countries, with the original revision becoming known as low-band or Lo-band. This was followed by SP (superior performance), for NTSC and PAL countries. Both revisions increased the FM carrier frequencies, increasing the available bandwidth on the tape, hence increasing image quality and the number of lines. SP also introduced chrome dioxide tape. Hi-band U-matic recordings will play in black and white in Lo-band U-matic machines. PAL U-matic hi-band increased the FM carrier frequency to 4.8-6.4 MHz, while U-matic SP increased it even further to 5.6-7.2 MHz, while increasing the color carrier frequency to 924 kHz. U-matic tape moves at 3.75 inches per second, and has a tape writing speed of 8.54 meters per second for PAL or 10.26 for NTSC. This means that the heads on the drums of U-matic VCRs move across the tape at one of those speeds. The drum has two heads, both of which are used for recording video. The drum spins at 1500 rpm for PAL or 1800 rpm for NTSC. U-matic low-band when recording NTSC has a sync tip frequency of 3.8 MHz, a peak white frequency of 5.4 MHz, and a color carrier frequency of 688.373 kHz. NTSC U-matic SP has a peak white frequency of 7 MHz. When recording PAL, U-matic Hi-band had a sync tip frequency of 4.8 MHz, a peak white frequency of 6.4 MHz, and a color carrier frequency of 983.803 kHz, while U-matic Hi-Band SP had a sync tip frequency of 5.6 MHz, and a peak white frequency of 7.2 MHz, retaining the color carrier frequency of regular Hi-band. Introduction At the 1971 introduction of U-Matic, Sony originally intended it to be a videocassette format oriented at the consumer market. This proved to be something of a failure, because of the high manufacturing cost and resulting retail price of the format's first VCRs. But the cost was affordable enough for industrial and institutional customers, where the format was very successful for such applications as business communication and educational television. As a result, Sony shifted U-Matic's marketing to the industrial, professional, and educational sectors. U-Matic saw even more success from the television broadcast industry in the mid-1970s, when a number of local TV stations and national TV networks used the format when its first portable model, the