基于89C52单片机的环境噪声监测，数模转换用的是LM331所构建的打电压频率转换电路。-Based on 89C52 environmental noise monitoring, digital-to-analog conversion is playing the voltage frequency conversion circuit LM331 built.

单片机的各种外接硬件如译码器，锁存器，液晶显示器，等着各种企业各种型号的硬件管脚使用说明书，是搞单片机应用的必备手册-All external hardware such as single chip decoder, latch, LCD, wait for all kinds of enterprises of various types of hardware pin manual, is essential to engage in manual SCM application