Abstract: The Eight-to-Fourteen-Modulation (EFM) circuit for a digital audio disc system. The circuit stores in a separate memory the numbers of leading and trailing zeros, and the code sum values and the inverting informations for each channel bit data with the merge bit data corresponding to 8-bit symbol data. The circuit sequentially reads the informations of the memory and compares the informations for four merge bits, thereby rapidly selecting an optimum merge bit to satisfy the run length restriction and the minimum direct current requirement.Therefore, the circuit enables a real time process of the EFM conversion, a miniaturization and economization of the system due to the reduction of the number of the hardware.