Position feedback system

A position feedback system adapted to return a detection signal of a measuring device provided on the side of a machine tool to an NC apparatus to determine the working position of the machine tool when the machine tool is controlled by a command signal from said NC apparatus comprising:

• a counter means adapted to carry out the up-counting and down-counting of a counting pulse formed on the measuring device side and used to discriminate the direction of movement and detect the amount of movement;
• a comparator means for carrying out the comparison between the counted value of said counter means and a predetermined reference value;
• and
• a pulse generating means adapted to output one counting pulse for up-counting or one counting pulse for down-counting to said NC apparatus side at a time period larger than a minimum time period necessary for said NC apparatus side to carry out the signal reading operation, and supply said counting pulse for up-counting as a down-count input to said counter means and return said counting pulse for down-counting as an up-count input to said counter means;
• whereby said counting pulse is output from said pulse generating means to said NC apparatus die until said counted value of said counter means becomes the same as the reference value of said comparator means.