The CTS-1 was Sharp's first office computer and went on sale in 1962. It consisted of a paper-punch typewriter and a relay computer. Using biquinary notation with seven bits representing one decimal digit, it could carry out addition, subtraction, multiplication, and other arithmetic operations and control printing. Forms were selected by program, and two programs working with different forms could be loaded simultaneously. A switch was used to select between the two programs.

The CTS-1 was mainly supplied to large textile manufacturers, trading companies, and city banks.