Data reading apparatus for data transmission

Claim 1

A data reading apparatus for data transmission, for reading digital data from a digital signal series obtained by comparing the level of an incoming transmission signal obtained through a transmission path with a reference level at a detector, said data reading apparatus comprising: a reference clock pulse generator for generating a reference clock pulse having a period equal to substantially 1/M (M is an integer greater than or equal to two) of a transmission digit period of said digital signal series; detecting means supplied with said digital signal series and said reference clock pulse generated by said reference clock pulse generator, for generating a level variation detection pulse in phase synchronism with level varying points corresponding to rising edges and/or falling edges of said digital signal series; frequency dividing means reset by said level variation detection pulse from said detecting means, for generating a data reading timing clock pulse with a period substantially equal to the digit period of said digital signal series and with a phase delayed with respect to said level variation detection pulse, by frequency-dividing said reference clock pulse from said reference clock pulse generator; and a data reading circuit for obtaining a data reading output signal by latching said digital signal series by said data reading timing clock pulse obtained from said frequency dividing means, said frequency dividing means comprising phase controlling means for generating said data reading timing clock pulse variably controlled of a phase delay quantity with respect to said level variation detection pulse, according to a value of the data reading output signal in a digit immediately preceding a digit from which the data reading output signal of said digital signal series is obtained.