CTIFREE manufactures electronic office supplies, specializing in scientific and engineering calculators designed for students, educators, and professionals.
CTIFREE is a consumer electronics brand operated by Guangzhou Cania Technology Co., Ltd., best known for its line of scientific and engineering calculators. The brand provides affordable, high-functionality alternatives to major calculator manufacturers, catering to the needs of mathematics and science students as well as professionals.
Popular models like the FX-991MS and FC-991ES PLUS feature comprehensive function sets, including equation solving, complex number calculations, and statistical capabilities. CTIFREE products are typically characterized by dual power sources (solar and battery), durable build quality, and user-friendly interfaces suitable for academic examinations and daily office use.
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To reset most CTIFREE scientific calculators, try pressing 'SHIFT', then 'CLR' (usually the 9 or Mode key), select 'All' (usually option 3), and then press '='. Alternatively, look for a small reset button on the back of the device.
Remove the screws on the back case to access the battery compartment. Replace the old battery (typically an LR44 or similar button cell) with a new one, ensuring the correct polarity, and close the case securely.
A dim or blank screen usually indicates that the battery is low or the solar panel is not receiving enough light. Move to a brighter area or replace the battery if the issue persists.
Yes, the FX-991MS model typically includes an equation mode. Press the 'MODE' button repeatedly until 'EQN' appears, then follow the on-screen prompts to input the coefficients for your equation.