What does this lock button do?

Is it

|-| = Choke

)-( = throttle

subtle difference ?

I asked my mechanic about this once and he said it was for when you were towing something, you can use it to keep the revs up (ie hand throttle)..... suppose to make towing easier. I use it for early morning start instead

I guess you can use it for what you like but on a 4X4 it's main function is for rock crawling, to stop your foot bouncing on the throttle when you bounce around in the cab.

G'day mates

Thank you everyone for making this thing clear as i was also wondering about its function. Can anybody please lemme know that how it operates? is it operated electronically or through a cable wire? as its not working in my GQ TD42.

G'day Gman,
on my old GQ it was manual. A wire behind the 'button' went back to the fuel flow control under the bonnet and you simply pulled it towards you then twisted it and it gripped in position thus overriding the accellerator and setting a higher engine rev. speed.
If it's not working it's possibly because the adjustment, made by a simple lock screw device on the end of the cable under the bonnet, is out of position. Easily corrected by relocking the adjuster in place after feeding more cable through. Don't set it so that your idle speed is increased though. Could be that the eccentric gripping system on the knob is worn. Be a bit surprised but if so I reckon you're up for a new unit through the dashboard.
My later GQ has a slack arsed electronic button you push. No control at all and it's set up so it can't be used as a hand throttle. Hope you haven't got that metrosexual rubbish on your GQ.
Luck,
Col

It's cable driven if you pull it out you will see you right pedal pull down so it must link up to the throttle cable