| 摘要 |
PURPOSE:To avoid an error at slow speed if the quality of a medium in use is deteriorated by decreasing or increasing the frequency of a reference signal depending whether the error rate of data transmission/reception is higher than an upper reference value or lower than a lower reference value. CONSTITUTION:A reference signal source 1 of frequency variable is set, e.g., 1,200Hz at first and a reference signal source of an opposite data transmitter is set also to 1,200Hz. In starting reception of data, the data transmission speed is 1,200bps. When data is demodulated by a modulator-demodulator 2 and sent to a computer 4, an erroneous number is counted. When the erroneous number is higher than the upper limit reference voltage, an instruction is issued to a controller 3 to decrease the frequency of the reference signal by one rank. When the erroneous number is lower than the lower limit reference value, an instruction is issued to the controller 3 to increase the frequency of the reference signal by one rank.
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