When you look under the dashboard you will see the fuse box, this isn't just a fuse box though.
This box contains a lot of electronics that control almost all of the electrics in the car.
SAM - Signal Acquisition & Actuation Module - Footwell fusebox in newer smarts.
ZEE - Zentrale Einschub Elektrik (Central Electric Module) fusebox in older smarts.
If you have a 600cc smart fortwo, you have a ZEE.
If you have a 700cc smart fortwo, you have a SAM.
If you have a Roadster, you have a SAM.
If you have a 999cc fortwo (new style), you have a SAM.
If you have an 800cc diesel fortwo then it depends on the build date.
Up until about 2004 they had the ZEE and after that it had the SAM.
The problem is that this differs depending on where you are in the world. Best thing to do is look.
Below is a ZEE unit fuse box. This particular one has a trust plug in the OBD port.
It is easy to distinguish over the other type of fuse box because the ZEE has visible relays.
These small boxes are scattered over the face of it and do a lot of the switching.
Below is the SAM unit, you can see the obvious difference between that and the ZEE.
The SAM unit fuse box face only shows fuses, all of the relays are internal.
The other giveaway is that is has SAM written on the label.