普通电话机改为投币定时电话机张国全许多单位想控制电话的使用率和通话时间，但是现有的投币电话机价格昂贵，而且须邮电部门批准才能安装。因此，在不破坏原电话机的前提下，用外加辅助电话的方法，把普通电话机改成投币定时电话机，是一种较合理的方法。本文介绍简单实... Ordinary telephones changed to coin-operated timed telephones Many units of Zhang Guochuan wanted to control phone usage and talk time, but existing payphones are expensive and require approval from post and telecommunications authorities for installation. Therefore, without breaking the original telephone under the premise of using additional telephone methods, the ordinary telephone into coin-time telephone, is a more reasonable approach. This article describes the simple ...