引言电视会议和电视电话业务是一种新的业务,它要求占用比特率高于电话业务。在CCITT对ISDN和国际间互连的研究中,已经发现384 kbit/s速率是宽带业务中一种最重要的信道容量。在此基础上电视会议和电视电话业务应以384 kbit/s速率的倍数为基准。应该注意,2048 kbit/s和1544 kbit/s数字一次群可以分别用公式y+(n×384)kbit/s来表示,式中n=5或4,y=128或8 kbit/s。本建议仅涉及数字一次群传输的帧结构,并未建议排除掉用其他帧结构或基群格式或更 Introduction Videoconference and videophone services are a new type of service that requires a higher bit-rate than telephone service. In the CCITT study of ISDN and international interconnections, it has been found that the 384 kbit / s rate is one of the most important channel capacities in broadband services. On this basis, videoconferencing and videophone services should be based on a multiple of 384 kbit / s. It should be noted that the digital primary groups of 2048 kbit / s and 1544 kbit / s can be represented by the formula y + (n × 384) kbit / s, respectively, where n = 5 or 4, y = 128 or 8 kbit / s. This Recommendation deals only with the frame structure of digital first-group transmissions and does not suggest excluding the use of other frame structures or base-class formats or more