B2 is avionics. this may help, not used them myself however
http://www.part66.com/content/public...ance/default.a
Details here on what is what and what is required,
Category B1 and B2 Licences - The Cardiff and Vale College - International Centre for Aerospace Training
bits of the licences will be changing, see
http://www.pprune.org/engineers-tech...part-66-a.html
Avionics will also in future cover Electrics as well....
Hope they help.