such as Pang/Buster Bros use an encrypted "Kabuki" Z80 CPU manufactured by VLSI Technology, where the decryption keys are stored in its internal battery-backed memory, to avoid piracy and illegal bootleg games. Notable uses Desktop computers During the late 1970s and early 1980s, the Z80 was used in a great number of fairly anonymous business-oriented machines with the CP/M operating system, a combination that dominated the market at the time. Four well-known examples of Z80 business computers running CP/M are the Heathkit H89, the portable Osborne 1, the Kaypro series, and the Epson QX-10. Less well-known was the expensive high-end Otrona Attache. Some systems used multi-tasking operating system software (like MP/M or Morrow's Micronix) to share the one processor between several concurrent users. Multiple home computers were introduced that used the Z80 as the main processor or as a plug-in option to allow access to software written for the Z80. Notable are the TRS-80 series, including the original model (later retronymed "Model I"), Model II, Model III, and Model 4, which were equipped with a Z80 as their main processor, and some (but not all) other TRS-80 models which used the Z80 as either the main or a secondary processor. Other notable machines were the DEC Rainbow 100, and the Seequa Chameleon, both of which featured both an Intel 8088 and a Z80 CPU, to support either 8-bit CP/M-80 applications running on the Z80, or a custom MS-DOS that was not fully compatible with PC DOS applications running on the 8088. In 1981, Multitech (later to become Acer) introduced the Microprofessor I, a simple and inexpensive training system for the Z80 microprocessor. Currently, it is still manufactured and sold by Flite Electronics International Limited in Southampton, England. In 1984 Toshiba introduced the Toshiba MSX HX-10 in Japan and Australia. In 1985, Sharp introduced the Hotbit and Gradiente introduced the Expert, which became the dominant 8-bit home computers in Brazil until the late 1980s. Portable and handheld computers Use of the Z80 in lighter, battery-operated devices became more widespread with the availability of CMOS versions of the processor. It also inspired the development of other CMOS based processors, such as the LH5801 from Sharp. The Sharp PC-1500, a BASIC-programmable pocket computer was released in 1981, followed by the improved Sharp PC-1600 in 1986 and the Sharp PC-E220 in 1991. Later models of the Sharp Wizard series of personal organizers also were