窄带ＩＳＤＮ与宽带ＩＳＤＮ马秀芳随着电信事业的发展，我们周围的电信设备越来越多，如电话机、电传打字机、传真机、调制解调器等。虽然它们的用户线路看来相同，但在电信部门内部却要作不同的信息处理，连到不同的电信网，例如电话网、用户电报网、数据通信网等。电话... Narrowband ISDN and Broadband ISDN Ma Xiufang With the development of telecom industry, more and more telecom equipment around us, such as telephones, teletypewriters, fax machines, modems and so on. Although their subscriber lines appear to be the same, they have to be handled differently in the telecommunications sector, connecting to different telecommunications networks such as telephone networks, telegraph networks and data communications networks. phone...