Tele-satellite had a good article recently
What DiSEqC Do You Need?
1. No DiSEqC is good for single antenna systems that are fixed on one satellite. Every receiver can handle this.
2. Tone Burst is used for the simultaneous reception of two satellites with a monoblock LNB. This switching criteria is supported by every digital receiver.
3. DiSEqC 1.0 is for multifeed and/or multi-antenna systems with up to four LNBs/antennas. This expansion of Tone Burst can operate four to eight switches.
4. DiSEqC 1.1 is for multifeed systems with cascading multiswitches. This expansion of DiSEqC 1.0 can switch between up to 56 satellite signals. Control commands are repeated multiple times to guarantee that they reach every switch level. It is usually only used with larger antenna systems.
5. DiSEqC 1.2 drives H-H antenna motors so that all of your favorite satellites can be received. It has some weaknesses with regards to storing satellite positions.
6. DiSEqC 1.3 also drives H-H motors. With the position calculations built into the receiver, it takes full advantage of the DiSEqC 1.2 GoTo X commands. These receivers are labeled with USALS, DiSEqC 1.3 or GoTo X.