Many consider ReVox open-reel tape recorders to be high-end audio equipment. The most famous of these are the G36 (valve type), A77 (solid state with relay controls) and B77 (solid state with logic control and direct-drive). The A700 was the top of the line 1970s machine with 3-speed quartz PLL capstan, or, like the B77 which appeared in 1979, variable tape speed from 2.5 to 22.5 inches per second. Pictured to the right is the PR99 Mk2, a variant of the B77 for professional users, differing from the B77 in having balanced line in/out, and a real-time counter and auto-locator. The PR99 series was superseded by the C270 series, available also in multi-track formats (C274, C278).