Quoted from revmex:
Or does it only light on when it has established connection with a PC or reading/writing?
It only lights when the PC connects to it. Its a very good programmer, but you (may) need DOS and a parallel port and may need an older PC. They also use identity cards that plug into the side--which is how it routes power, etc., for the type of chip you're burning. Make sure you have the right card installed for the type of chip you're burning. Just wanted to mention that, in case you bought it used, and didn't get the cards with it.
I've had my EMP10 for 15+ years and it has never failed to burn a chip. They're so good, it's worth keeping an old DOS machine, just for the burner IMHO. They also handle some of the oddball chips, like 2716's, 2516's, 2532's, etc.
The EMPs were built around 1997. They do not work with some newer PCs, because of a timing issue between the EMP10 and the newer motherboard UARTs. That said, I was pleasantly surprised when my EMP10 worked with my ASUS M4A88T-M motherboard (circa 2010). I boot to a FreeDOS partition using GRUB to select it at startup.
So you may have to try several PCs or older laptops to find one that works for you, but even newer PCs can work, you just have to try until you find one that works satisfactorily. There are some people that have gotten it to work under XP, but I've not had luck with that, and don't run XP anymore anyway.
Here is a good info page with links to several versions of the EMP software:
Also if you search for 'EMP 10' you may find other useful info.