内线电话赵玉安本文介绍一种将玩具电话机稍加改进，即可投入使用的内线电话。它具有成本低、无需交换机等特点，可广泛应用于机关、学校、医院等场所，大大提高工作效率。一、工作原理本电话机由电话组件、编解码电路和振铃电路所组成（见图）。下面以电路图中甲方为例加... Interphone Zhao Yuan This article describes a toy phone will be slightly improved, you can put into use the intercom. It has the characteristics of low cost, no switch, etc., which can be widely used in institutions, schools, hospitals and other places, greatly improving work efficiency. First, the working principle of the phone by the phone components, codec circuit and ring circuit (see Figure). The following circuit in the party as an example plus ...