| 摘要 |
PURPOSE:To automatically discriminate the communication speed by counting clock pulses in the period when the start bit signal of an RS-232C is generated. CONSTITUTION:A CPU 5 receives an output Q2 of a flip flop 4 by an end signal terminal END and discriminates the communication speed by the counted value of a counter at this time. A transmission speed of a transmission signal, the inverse of SD of the RS-232C can be transmitted at 1200bps and 300bps communication speeds, and the frequency of the clock of a pulse generator 1 is set to 10kHz. The counted value of the counter 2 is 9 or 8 in the case of 1200bps communication speed and is 34 or 33 in the case of 300bps communication speed. The CPU 5 discriminates 1200bps or 300bps communication speed in accordance with the counted value and outputs a communication speed switching signal or the like based on the discrimination result to a network control unit NCU and a MODEM.
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