76 srv 240 trim switch question

[Lake Erie Monster]

on my 76 srv 240 i have a very different switch for controlling the outdrive trim. this one has 3 buttons, can some one explain this to me, my last boat was an 87 bayliner ciera 2550 and it only had a toggle up and down switch.

 

[moparlvr4406]

the upper button is tilt up
the middle button lowers the unit down to the "trim" position
the bottom button lowers the unit even farther down for actual trim adjustments