How hard is the maths in Telec or elec eng ?
Like any other engineering course, it's very heavily dependent on maths.
The assumed knowledge for the course is HSC Maths Ext 1 (3U), which means that if you have done lower than that (e.g. 2U maths), they won't stop you from getting in, but it's strongly recommended you do a bridging course in this case because when the lectures start they assume you're completely familiar with the 3U stuff (which is covered in the bridging course).
If you've done 4U maths, then you shouldn't find the maths too hard. In fact, there's two types of maths classes, there's Maths & Higher Maths. Higher Maths is for students who've done 4U and also done well in it, it's an extension type of subject which is harder than normal Maths, but you get scaled up to compensate for it (like 4U does in the HSC). The Higher Maths classes learn exactly the same stuff as normal Maths, plus a few extra advanced topics & harder applications of the standard stuff.
i THINK i really want to work with wireless technology and data transfer and stuff..
Electrical is like a combination of electronics, energy systems, signal processing, telecommunications etc. Telecommunications is similar but it focuses more on the telecommunications & electronics stuff. The first year subjects are exactly the same. If you want to see all the subjects that are done in elec & telecomms, then look here:
http://www.eet.unsw.edu.au/programs/undergraduate.html