| 摘要 |
An interface unit connected between a telephone and a telephone network sets a data transmission speed to an optimum speed. The interface unit transmits a type query signal to the telephone terminal at a first speed. The telephone terminal transmits a type signal to the interface unit at the first speed in response to the type query signal. When the interface unit receives the type signal from the telephone terminal, the interface unit changes a transmission speed to a second speed higher than the first speed if the received type signal indicates that the telephone terminal is capable of transmitting data at the second speed. The interface unit also transmits a speed change request to the telephone terminal at the second speed.
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