To add on the other solution, it seems using the S.E.D Jumper to revive a fallen S.E.D as an Engineer also counts as a revive since it popped after reviving a S.E.D
EDIT: Seems the other guide was deleted. Odd
Well, just revive teammates in Co-op or Versus matches by playing as a medic and using defibs on dead teammates, or by playing as an engineer and using the S.E.D jumper on dead S.E.D's