An automatic test circuit for simultaneously testing a plurality of data sets wherein the test circuit provided for each data set a multiphase program which includes sending test signals to the data set and measuring the distortion of signal received from the data set. During a measuring phase the test circuit enables each data set to contend for a common measuring circuit to apply signals to the measuring circuit upon seizure thereof and to thereafter release from the measuring circuit in response to a signal from the data set. The test circuit then either advances to the next program phase if the distortion of the measured signals is below a predetermined threshold level or again bids for the measuring circuit to repeat the measuring phase if the distortion exceeds the threshold level.