交换机的作用

交换”和“交换机”最早起源于电话通讯系统（PSTN）。我们以前经常在电影或电视中看到一些老的影片时常看到有人在电话机旁狂摇几下（注意不是拨号），然后就说：跟我接XXX，话务接线员接到要求后就会把相应端线头插在要接的端子上，即可通话。其实这就是最原始的电话交换机系统，只不过它是一种人工电话交换系统，不是自动的，也不是我们今天要谈的程控交换机，但是我们现在要讲的程控交换机也就是在这个电话交换机技术上发展而来的。

含税运的价格，货源充足，价格稳定！

BLACKBOX 目录产品分为几大类：

1. KVM 多电脑切换器 和 KVM 延长器 
2. 全自动、手动线路转换 - 包括 RS232, 
V.35, BNC, RJ11, RJ45 等
3. 电缆和基建 - 包括各类双绞线、铜轴电缆
、各种接线头
4. 测试仪和工具 - 网络测试仪、网线、光纤
测试仪、做线工具等
5. 机柜 - 挂墙式、落地式、大型、小型等
6. 电源和防雷保护器 - 含远程电源管理，电
源、线路防雷保护器
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