fast old fart
They can be found in the australian racing, Castle hill offroad thread.
We run personals and handouts every club meeting. Complete with sound etc. From a laptop.
Sorry I am not 100% sure so I won't say brands etc. But any of those guys will be able to point you in the right direction.
We have a loop allways in the ground. And just plug in come race day.
Hope this helps. Our leads to it.