在电影、电视中常看到有一种带拉杆天线的电话机。主人用它打电话可以满屋子走。这种不需要电话线的电话叫“无绳电话”。没有电话线怎能打电话,原来在这台电话机里装有一套袖珍式无线电收发信机,在室内墙壁上或住宅的其它地点(距离电话机20米左右)也安装上一套无线电收发信机作为“中转站”。“中转站”与电话局之间有电话线联通。用户打电话时,电话机送出的拨号脉冲和话音信号经过无线电台转换成相应的电磁波,发往“中转 In the movies, television often see a telephone with a telescopic antenna. The owner can use it to call the room to go. This does not require a telephone line called ”cordless phone “. There is no telephone line how to make a call. It is supposed that a pocket-sized radio transceiver is installed in this telephone set. A radio transceiver is also installed on the wall of the room or at other places in the house (about 20 meters away from the telephone) Machine as ”transfer station “. ”Transfer Station “ and the telephone exchange between the telephone line. When a user calls, the dial pulse and voice signal sent by the telephone are converted to the corresponding electromagnetic waves by a radio station and sent to the ”