Abstract: Errors in determining a measured voltage are mathematically canceled in an analog-to-digital converter circuit useful for dual slope type using positive and negative values of a reference voltage. The errors are due to the off-set voltages inherent to operational amplifiers employed for an integrator and a comparator included within the analog-to-digital converter circuit. A counter circuit is provided for storing time information related to first and second dual slopes. A mathematical calculation is conducted with the aid of all the time information of the first and second dual slopes, whereby the measured voltage can be determined with eliminating the influence by the off-set voltage.

Abstract: A read only memory (ROM) is provided for storing digital information related to stitch patterns and control instructions for stitch formation purposes. A keyboard means is provided for selecting a desired stitch pattern and control instruction stored in the ROM. Selected digital information is introduced into a random access memory (RAM) and temporarily stored therein. The RAM develops control signals for controlling the needle position and the work feed in accordance with the control instruction selected through the keyboard means.