SPS is the company that I use.

There's 2 batteries in a 4DTV receiver: 1 on the main board of the unit that maintains the
digital unit I.D. number, and another inside the VCIIplus module, that maintains the
analog unit ID number. Don't worry about the VCII one, because at the end of this year, there will be no more analog subscription channels. If the one on the main board dies, and the unit loses AC power, it will lose the digital ID, rendering the receiver useless.