The Term MAC Stands For The Acronym: Multiplexed Analogue Components
A-MAC = This system offers multiplexed audio and data on a subcarrier(s)
combined with video before modulation. There are both video and bandwidth and threshold extension potentials.
B-MAC = This system multiplexes data and audio at baseband and color which is
transmitted sequentially, much like French SECAM (sequential with memory), red, then blue.
C-MAC = This system time multiplexes data at RF during line blanking digitally,
baseband modulating the carrier during the line scan.
D-MAC = This system frequency
multiplexes data at RF and video centered at 70 MHz. Video may be transmitted
from seperate locations. Two earth station receivers, however, are required
to decode and display
A-MAC - Unknown (Not Widely Used)
B-MAC - Used In North America, Australia & South Africa (525 Lines)