Watch this YouTube video
How To Extend Brother Printer Laser Toner Cartridge Life, and see
Toner Reset Instruction for Brother TN620/TN650.
I particularly like Brother laser printers as they are durable, and print fast. Very economical to operate. In fact, I have five of them, only one I bought new. Found the rest in thrift shops for $10. All wireless/network.
Just wanted to extract the toner cartridges and drums, but after some self servicing, discovered that they all work. So now when running out of toner, I just swap out the printer. :B Refill when I have the time.
BTW, this toner saver trick works great. Have been using my current Brother for 3 months after the toner so called was out. :S