The modem modulates the binary data into an analog signal at the source and demodulates the analog signal at the destination to binary data. 数据机在来源端调变二进位的资料进入的类比信号内并且在目的端解调这个类比信号成为二进位的资料。
When intermittent, low-volume data transfers are needed, modems and analog dialed telephone lines provide low capacity and dedicated switched connections. 当间歇性,低量的资料传输被需要时,数据机和类比的拨号电话线提供了低容量且专用的交换连接。