1. IN COMBINATION IN A SYSTEM FOR CONVERTING ANALOG SIGNALS INTO DIGITAL REPRESENTATIONS THEREOF, A SOURCE OF CONTINUOUS ANALOG SIGNALS CHARACTERIZED BY INTELLIGENCEBEARING AMPLITUDE VARIATIONS, REVERSIBLE COUNTING MEANS, ERROR AMPLIFIER MEANS RESPONSIVE TO ANALOG SIGNALS TO BE CONVERTED AND TO OUTPUT SIGNALS OF THE CONTINUOUS ANALOG TYPE FROM SAID ANALOG SIGNAL SOURCE AND SAID COUNTING MEANS, RESPECTIVELY, FOR SUPPLYING BIPOLAR ANALOG TYPE ERROR SIGNALS INDICATIVE OF THE RELATIONSHIP BETWEEN SAID ANALOG SIGNALS AND SAID OUTPUT SIGNALS, AND PULSE MEANS RESPONSIVE TO SAID ERROR SIGNALS FOR SUPPLYING TO SAID COUNTING MEANS PULSES WHOSE REPETITION RATE AND POLARITY ARE A FUNCTION OF SAID ERROR SIGNALS.