PURPOSE: To decide the operation of decoding section to be normal by storing a digital sine wave signal in a short time in a memory, repeating this operation to input the result to an encoding section, and inputting the outputted encoded code to a decoding section to make the difference between the level of an output signal and the level of an input sine wave signal constant.
CONSTITUTION: When testing an encoder and a decoder, switching devices 7 and 8 are connected by a signal route T1 including an encoding section 2, and digital since wave signals from a testing circuit 5 are inputted to the switching device 7, and returned signals are inputted to the switching section 8 through the encoding section 2. A part of output from the switching device 7 is inputted to a decoding section 3 through an A/D converter 1, switching device 6 and a D/A converter 4. The output is sent to the switching section 8 and the difference between signal level of the encoding section 2 and decoding section 3 is detected. At this time, if the difference is within a fixed limit, operation of the encoder and decoder is judged as normal, and when out of the limits, an alarm signal 15 is sent out.
| JPS62101126 | RIPPLE ELIMINATING CIRCUIT |
| JPS56166627 | DIGITAL-TO-ANALOG CONVERTER |
KO MASAHIRO
MAEDA YOICHI
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