| 摘要 |
The present invention is intended to transmit and receive desired data at low communication cost by selecting Recommendation T.30 in accordance with the estimation of line condition during the execution of procedures of Recommendations V.8 and V.34. At a calling station, when a JM signal is not detected within a CM signal transmission time t1, when a phase 2 signal is not detected within a time t2 after the end of V.8, when a phase 3 signal is not detected within a time t3 after the end of the phase 2, when a phase 4 signal is not detected within a time t4 after the end of the phase 3, when a phase 6 signal is not detected within a time t5 after the end of the phase 5, or when the phase 4 signal is not detected within a time t6 after the end of the phases 6 and C, it is presumed that the line condition is improper and a procedure of Recommendation T.30 is executed. At a called station, when a CJ signal is not detected within a JM signal transmission time t7, when the phase 2 signal is not detected within a time t8 after the end of Recommendation V.8, when the phase 3 signal is not detected within a time t9 after the end of the phase 2, when the phase 4 signal is not detected within a time t10 after the end of the phase 3, when the phase 6 signal is not detected within a time t11 after the end of the phase 5, or when the phase 4 signal is not detected within a time t12 after the end of the phases 6 and C, it is presumed that the line condition is improper, and the procedure of Recommendation T.30 is executed.
|
