| 摘要 |
PURPOSE:To prevent the lowering in the efficiency of data transmission and to reduce the number of control lines, by automatically switching the modulation and demodulation operation accompanied with the alteration of communication speed with the frequency identification of transmission timing signal. CONSTITUTION:The transmission timing signal input from the terminal 1 is fed to the frequency identifier 4. Further, when the frequency of timing signal is at 9,600Hz, on signal is output on the signal line A and at 4,800Hz on the line B and 2,400Hz, on the line C. The modulation and demodulation section 5 performs specified modulation and demodulation operation with the CCITT recommendation V29 at the on signal on the line A, with the recommendation V27 at on signal on the line B and with the recommendation V26 at on signal on the line C. |
