Tristar DLC was, as has been said, PFM.
When flaps were selected into the Landing range, the spoilers popped up to a null point (on the early models) of 7 degrees. Thereafter when pitch inputs were made, the spoilers would deploy further - up to 14 degrees for pitch down inputs and down to zero for pitch up inputs. (those were MAXIMUM values and were applied pro rata to the amount of pitch input). The effect, therefore, was to provide vertical positional change with minimum pitch disturbance.
The null position was increased on the 500s to 9 degrees(if memory serves correctly) with a similar operating function. The other active controls bit was effectively using the ailerons to provide gust load alleviation by means of a clever piece of kit detecting gusts as soon as the aircraft felt it at the nose and providing an aileron droop to compensate immediately.
The Tablets of Stone are lurking at home somwhere if you need chapter and verse from the Tech Authors.
