Program for using an IBM PC to read quadrature encoders through the parallel port (requires bi-directional port) and display position data on-screen.

计划使用IBM的PC阅读正交编码器通过并行端口（需要双向端口）和显示位置数据在屏幕上。

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The construction of concentric bi-directional valve overcomes the disadvantage of easy to connect between two parallel check valves.

同心双向阀结构克服了传统的单向阀并联结构两阀间易连通的缺点。

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EPP is a bi directional data communication protocol of enhanced parallel port, it has performances of high speed and easy extensibility, which is provided by luggable computer.

EPP是双向数据传输的增强并行口协议，速度较高，扩展方便，手提电脑均支持。

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