What is servotronic? Does my car have it?

I have a '95 - 540ia (build date 7/95) with 150K miles. My steering has developed the infamous loose on-center problem. I've talked with my independent mechanic, another well known suspension mechanic, and the dealer in my city about fixing the problem.
The 2 indy's say that adjusting the steering box in "just about impossible" on the V8 cars. And from what other threads I've read on this forum, I have to say I'm not to optimistic about the adjustment procedure.

The dealer says NO - They only replace the box at about $2700!!! OUCH!

I've looked online to see what a new or rebuilt steer box would cost. There are 2 kinds listed: 1. w/ servotronic for $1250-1550, or 2. w/o servotronic for $550.

Again what is servotronic?