Introduction The members of the MAC/packet family The MAC/packet family of systems consists of the fol.lowing three members: C-MAC/packet@ D-MAC/packet@ D2-MAC/packet. These systems incorporate the following common features: -time-division multiplexing -MAC picture coding@ with the capacity for extended aspect ratio and enhanced picture quality -packet multiplexing for sound and data -digital high and medium quality sound coding and error-protection method - service identification - conditional access with Video@ sound and data scrambling - full-channel digital mode of operation. The clock frequencies used in these systems have simple relationships with the sampling frequencies of the digital studio standard defined in CCIR Recommendation 601. The specification of the three .. mbers of the MAC/packet family is given in EBU doc. Tech. 3258@ 2nd issue. The present document is only concerned with the D-MAC/packet system.