早期的网桥、协议转换器和路由器都是简单的专用硬件设备，通常是通过直接连接到该设备本身串口的终端来配置的。
Early network Bridges, protocol converters, and routers were simple dedicated hardware units typically configured through a terminal directly connected to a serial port on the unit itself.
模数转换器是模拟电路和数字电路的接口，是手持终端中不可缺少的组成部分。
Analog to digital Converter is the interface of analog and digital circuit; it's an necessary part in the portable system.
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