三次群 meaning in English

tertiary group

Performance and test methods of the thirdorder digitalltiplex equipment operating at 3468 kbit sand using poive justification
34368 kbit s正码速调整三次群数字复用设备技术要求和测试方法
Specification for transmission of component - coded digital television signals for contribution - quality applications at the third hierarchical level
在三次群中传送馈送质量分量编码数字电视信号传输技术规范