根据使用目的不同,汽车电话可分为二大类:专用汽车电话和公用汽车电话.前者用于公安巡逻车辆通信、出租汽车调度、救护车联络等,直接采用语音呼叫,系统组成较单纯,依靠无线电通信技术就能够实现.后者则是接入市话网络的移动式公用电话,在行驶的汽车上能与市话网中的任一用户联系,甚至还能直接拨号打国内、国际长途电话.本文简单介绍一些国外有效利用公用汽车电话通信频率的技术. According to different purposes, car phones can be divided into two categories: private car phones and public car phones. The former is used for public security patrol vehicle communications, taxi scheduling, ambulance liaison, direct voice calls, the system consists of more simple, rely on The latter is achieved through the use of mobile telephones connected to the public switched telephone network, which can connect with any user in the local area network on a moving vehicle and can even directly dial domestic and international long distance calls. Briefly introduce some of the technologies that make effective use of the frequency of public car telephone communications.