Fixed TDM
A channel is divided into fixed-size slots
N sub-channels are multiplexed by assigning every Nth slot to the same sub-channel
- Slots usually have same same size, but it's sufficient for the sequence of slot sizes to be fixed
Ex.: 1.5 Mbit/sec T1 line
- 24 sub-channels and "frames" of 193 bits
- One bit marks the start of the frame, after which the first byte belongs to sub-channel 1, the second to sub-channel 2, etc.
- Slots are numbered from the start of the frame, and a sub-channel's slot number is its address -- addressing costs nothing
- Requires framing to find the start of the frame