Hey Thomas / Andy,
I have a Turbo HC, but according to the manual, both the Turbo & Non Turbo (NA) only have a Vacumm Advance when cold.
It pulls the Dizi about 25 deg advance (which seems heaps, but works) to help cold start. At approx 85c, the advance is switched off, and as Andy said, uses Cetrifugal Advance when warm.
The "Ignition amplifier" is only a switch, like points in a conventional car.
When the Reluctor (star thingie in the Dizi) passes the pick-up, it generates a small voltage.
The Module in the Ignition amplifier then switches the larger power on & off to the coil as required.
The Constant Energy Ignition or High Energy Ignition is used on many other cars, and you can google allot of info on the setup.
Other cars that use the system include many GM Cars, Land Rovers, Jaguar and many more, so is not a special "Lotus" system. The system can handle higher power than points (which burn out)
The Module inside the amplifier does fail from time-to-time, but fortunatly with GM parts and there performance upgrades common as mud, they are easy to replace.
It is interesting to note, that the OEM module in the Amplifier has "GM" on it
Drew