Sinclair's licensing agreement with Timex enabled the American company to produce three clones or offshoots of Sinclair machines for the US market. These were the Timex Sinclair 1000, Timex Sinclair 1500 (both variants of the ZX81) and the Timex Sinclair 2068 (a variant of the ZX Spectrum). The TS1000 was launched in July 1982 and sparked a massive surge of interest; at one point, the Timex phoneline was receiving over 5,000 calls an hour, 50,000 a week, inquiring about the machine or about microcomputers in general. It was virtually identical to the ZX81 save for re-branding and the addition of an extra 1 KB of memory, totalling 2 KB. In the five months following the TS1000's launch, the company sold 550,000 machines, earning Sinclair over $1.2 million in royalties.