区分住宅和商业应用中使用的简单楼宇对讲系统，以方便用户进行门禁控制，并包括安全应用的扩展功能。购买本文件时可获得的所有当前修订均包含在购买本文件中。

Differentiates between simple building intercom systems used in residential and commercial applications for the convenience of users for door entry control purposes, and includes extended functionality for security applications.All current amendments available at time of purchase are included with the purchase of this document.