Abstract: The transmission error measuring device comprises; a first counting circuit, a test data outputting circuit, a selecting circuit, a multiplexing circuit, a demultiplexing circuit, an arranging circuit, a data array monitoring circuit, a second counting circuit, a reference data outputting circuit, and a comparing circuit. When a test data outputted from the test data outputting circuit does not correspond to a reference data outputted from the reference data outputting circuit, the data array monitoring circuit rearranges the first count value by using a bit set at the bottom thereof in order to rearrange the test data.

Abstract: A bit error measurement circuit of the present invention which can measure for a bit error precisely. The bit error measurement circuit comprises: a memory circuit for memorizing one period data of a signal to be measured as a reference signal, an error detection circuit for detecting erroneous bits of the signal to be measured, an error counter for counting the erroneous bits detected by the error detection circuit, and a plurality of terminals for inputting a control signal to control the memory circuit from outside of the bit error measurement circuit; wherein the reference signal memorized in the memory circuit is inspected outside the bit error measurement circuit, and the erroneous bits are corrected on the basis of the control signal fed from the outside of bit error measurement circuit, when there are erroneous bits.