It's a CDMA Verizon tower base station that accepts common corded and cordless phones. $20 a month gets me local and long distance over 3G. No data or internet.
I bought one from Radio Shack and it was activated at the store. Received a phone call to someone who used to own that temporary number. Went home and spent 45 minutes on hold and talking to someone to get my old ATT number ported. That person didn't have an accent but didn't speak English (was reading from a script). After getting it home I couldn't make local or long distance calls without the device transferring me to an external operator and wanting to charge my credit card. I bought a service plan with this, that's not supposed to happen.
Second call to customer service and I get someone with an Indian accent but actual English speaker who tells me he knows what the problem is but does not have the authority to make the account change and transfers me to a woman who is a native English speaker and probably also American. She says there was something entered in the account info incorrectly and has me dial a number on the unit to reprogram it and it now works. She also answered a question about why the Net10 website would not let me enter a support ticket.
This is in bold because I've seen the same issue unresolved on an Amazon review. When Net10's website asks for the serial number of the unit, they are not asking for the serial number on the base of the unit,
they are actually asking for the MEID number directly above the actual serial number. 
The wall adapter supplied is 100-240vac 50/60Hz switching, 12vdc out. It's exactly 12vdc out, well regulated. The unit runs from the wall adapter when it is plugged and an internal 3.6v NiMH pack otherwise. The NiMH pack is charged to the raw edge of failure (4.3vdc+) I almost took it back for that reason. 4.05vdc is the proper long term limit for that kind of pack/chemistry. Yeah you get 10% less capacity that way but you don't cook the pack.
The unit will not run from my Wagan sine inverter. When I tried it the phone would only dial some numbers, like 9. 5 worked sometimes, 4 not at all. There was a dial tone. The wall adapter probably switched faster then the Wagan could keep up with.
I have 3 Harbor Freight pdus. A direct wire to the 6v and 9v outlets worked. I didn't want to try it on 12v for fear that would rise above 12v during the day. The 6v tap I use for a 12v fan so it runs slower and uses less power and doesn't drain my batteries at night. It charges and works correctly on 9v so that's where I'm leaving it.
I dropped my ATT dsl and use a Virgin Mobile 3G/4G Hotspot. I switched from ATT because they raised my phone+internet from $56 to $72 a month in the last 3 years and have given me nothing for it. The quality of ATT's network continues to decline as well. I used to get the 1.5 Mb/s rated throughput, now it's that fast for a few seconds and then it chokes and dies. The network in south Florida is dying from the traffic. The VM Hotspot sends my connection to Havana, Florida usually. It had me in Salinas, Kansas on day and Hotmail locked my web account because I appeared to be too far from home. Facebook locked me out one night after ATT routed my phone and internet to Atlanta and then Charlotte to route around a failed local circuit. If there is no local good connection because of traffic, I may as well not be paying premium prices.