To make a quantization code that is used for data transmission of pulse amplitude modulation effective by switching a D/A converter and an A/D converter of a device whose analog side is connected to a subscriber's line through a hybrid circuit to an operation through a logarithmic characteristic curve and an operation through a linear characteristic curve.
Converting devices 20 and 21 convert 12 to 16-bit width on the sides of a D/A converter 18 and an A/D converter 19 into the linear value of 8-bit width. Data is converted by a logarithmic quantization characteristic curve in the direction from an analog interface 12 to a digital interface 14 and is converted by the logarithmic quantization characteristic curve or a linear quantization characteristic curve in the direction a digital interface 13 to the interface 12. An identifying device 17 controls the device 20 based on a modem signal after modem connection is formed and when pulse amplitude modulation is determined, the device 20 is switched to the linear quantization characteristic curve. The logarithmic quantization characteristic curve is selected again as basic adjustment after connection is finished.
| JP2013030908 | RADIO RELAY DEVICE AND RADIO COMMUNICATION METHOD |
| JPH09297752 | DATA RECEIVER |
FRENZEL RUDI
HOEFER GERALD
