Have had a quick search and I understand what it does and where it might be useful.
Never used one, so where do I find it (Scania). Floor / Dash / Column? What symbol does it have? Give us a clue!
(Any other secondary brake info would be handy too)
Usually a switch on the dashboard on a Scania. Switch on and it comes on automatically.
Foot switch on some older trucks, for when you need it.
Extra stalk on some, like Volvo.
Depends what Scania you’re in…
In a smaller one there’s a switch on the dash marked “AUT”. Switch it on and the exhaust brake will opperate on the first section of brake pedal. (gentle application).
On the bigger Scania’s, there’s a seven stage lever on the dash.
Cheers for that. At least I’ll have some clues to “I wonder what that button does…” 
I’ll see what it’s like in the morning.
If you’re in a DAF then look for a little raised blob on the angled slope to the left of the clutch - press this and feel the force!! 
Actually, don’t bother… Just open your windows - you’ll get more retardation from the extra drag than DAF’s pathetic exhauster will ever give you! 
I’m wary of floor buttons because when I was learning in a Dennis 6sp coach, there was a cut-off switch on the floor in the middle just in front of the seat (and just where I like to plonk my foot when it’s not on the clutch.) Took 2 days to avoid killing the engine by accident.
I did see a blob on the floor of the DAF I drove the other day. Didn’t look like much to me though. It looked more like one of those many blobs you get on anti-slip flooring!
To me any buttons around the clutch pedal are are the good old 1960s headlamp dip switches.
Thanks for that, if I see one again, I’ll wind the windows down. 
In Buses all the Retarders are Hydraulic, with some of the newer ones such as the DAF/VDL Bus SB120 and SB180 being Electric Retarders - on Buses universally the Retarder is controlled through use of the Brake Pedal.
If you ever drive a Bus with a “Voith” automatic gearbox, when the Retarder in Use light comes on when you hit the brakes, there’s always a small delay before it actually activates…sometimes you can be sent through the windscreen!!
MCW Metrobus’ were famous for their Retarders, it either left you with a Forehead saying “MCW Metrobus” from the steering wheel, or it didn’t work at all!
Richard
