The 7 Best VoIP Adapters
Updated by · How we research
Seven VoIP phone adapters compared on provider lock-in, phone ports, fax support and 911 setup. The Grandstream HT801 v2 is our pick for most homes. When users buy our independently chosen editorial recommendations, we may earn commissions to help fund the Wiki.
A VoIP adapter turns an ordinary home phone into an internet phone, but the box alone isn't phone service. Some come bundled with their maker's service and can't move to another, while open adapters work with almost any provider once you type in a few settings. It's for anyone keeping a favorite handset or fax machine.
Editor's Notes
October 26, 2026, by Ezvid Wiki Editors:
The Obihai and Cisco adapters that once led this list are gone. Poly ended support for the OBi200 and OBi202 in 2023, and Cisco has retired the SPA112 and SPA122, so we rebuilt around what's sold new. The Grandstream HT801 v2 now leads because it is inexpensive, current and works with almost any provider, and the Grandstream HT802 v2 takes over from the older version of the same two-line model.
The Vonage box and the magicJack GO went too, one unavailable and one down to old stock. We added the Ooma Telo and the magicJack C528 for people who want the service bundled, plus the Grandstream HT812 v2 for anyone who needs a router built in. The Grandstream HT813 stays for households keeping a landline.
Nobody publishes lab tests of these little boxes, so we worked from Grandstream's spec pages, Ooma's and magicJack's service terms, a small-business roundup and the end-of-support notices for the older models.
Earlier notes
February 12, 2020, by Kaivaan Kermani:
This list didn’t need much updating, as there were some good ATA’s (Analog Telephone Adapters) here already. The list contains a reasonable mix of single-FXS (Foreign Exchange Station) ATA’s like the MagicJack Go and Obihai OBi200 and dual-FXS ATA’s, which pretty much account for all the other models in the list. I don’t have an issue with dual-FXS models dominating the list as they’re quite practical for office setups in case you need two phones or a phone and a fax machine. I did however think that this list could use an FXS/FXO option, so I’ve included the Grandstream Hybrid. The FXO stands for Foreign Exchange Office port, which basically ensures that you retain traditional landline access through a POTS (Plain Old Telephone System) line in the event that your Internet or VoIP system fails.
The list was also lacking any VoIP adapters with routers for people who can’t spare an Ethernet port on their modems or routers to plug in their VoIP systems. Thus, I’ve added the Cisco SPA122. Cisco and Grandstream are quite dominant brands in the ATA market and they make some great single and dual FXS models too, a few of which we’ve listed here. I’ve also updated the Ooma Telo Air to the Ooma Telo Air 2, which has built-in Wi-Fi, meaning that you don’t need to use a dongle to connect wirelessly, unlike with many other options. There are mixed reviews regarding the quality of wireless connections versus hard-wiring the ATA via its Ethernet port. I would suggest that you try both and see what works for you, though the Telo Air 2 does seem to produce a strong wireless signal.
Special Honors
VoIP.ms Open adapters need a provider, and VoIP.ms is a long-running choice among people who set up their own. It offers per-minute and flat-rate plans and publishes setup guides for common adapters, including Grandstream's. voip.ms
Open Adapter Or Service Box
A VoIP adapter, also called an analog telephone adapter or ATA, has a phone jack on one side and a network jack on the other.
A VoIP adapter, also called an analog telephone adapter or ATA, has a phone jack on one side and a network jack on the other. It turns the sound from an ordinary corded or cordless phone into internet calls. The box is only half of the setup, though. Something has to carry the calls, and that's where the two kinds split.
Open adapters such as the Grandstream HT801 work with nearly any provider that uses the standard SIP protocol: pay-per-minute services, flat-rate plans or an office phone system. You copy a server name, user name and password into the adapter's web page, and you can change providers whenever you like. That flexibility is why people who once bought an Obihai OBi200 or a Cisco SPA122 look to Grandstream now; Poly ended support for its OBi line in 2023, and Cisco's SPA adapters have been retired.
Service boxes such as the Ooma Telo and magicJack come with their maker's service already set up. Plug them in and the phone works, but the hardware can't be moved to another provider. Ooma charges no monthly service fee for basic U.S. calling, only taxes and fees, while magicJack includes a year and then asks for a renewal. If you'd rather never see a settings page, a service box is the easier path.
Ports, Routers, Fax And A Landline Backup
Count the phones first. A one-port adapter feeds one number, though that line can still ring several cordless handsets from one base. Two ports give two separate numbers, handy for a home office or a dedicated fax line. Grandstream's HT812 product page lists two phone ports, two gigabit network ports and a NAT router, so it can share one wall jack with a computer. For four or more phones, larger multi-port gateways exist, but most homes don't need one.
Fax is the weak spot of internet calling. A fax machine's tones get mangled by the compression that voice calls use, so look for T.38 fax relay, which the Grandstream adapters support with a plain fallback mode. Your provider has to support it too, and even then some faxes fail.
An FXO port connects the adapter to a copper landline. The HT813 uses it to switch calls to the landline when the internet is down, a feature Fit Small Business singles out in its adapter roundup. It only helps if you keep paying for that landline.
911, Power Outages And Security
Internet phone service handles emergencies differently from a landline. The FCC requires interconnected VoIP providers to offer 911, but the service relies on the address you register with your provider. If you take the adapter to a vacation home or move, update that address before you make calls from the new place. Ooma ties its 911 service to the address on your account, and magicJack says its app can't place emergency calls.
When the power or internet goes out, so does the phone. A small battery backup for the modem, router and adapter keeps calls going through short outages; Ooma sells a Telo model with a built-in battery, and the base Telo has none.
An open adapter stores your provider's password, so treat it like a router. Change the default admin password, keep the web page off the open internet, and install firmware updates. Grandstream asks HT802 v2 owners to run firmware 1.0.19.11 or newer. We found no recalls for any of these brands in the Consumer Product Safety Commission's database.
How we researched this
We compared 19 VoIP adapters, read Grandstream's spec pages and the service terms Ooma and magicJack publish, checked a small-business roundup and the end-of-support notices for discontinued Obihai and Cisco models, looked at long-term owner feedback, and checked every brand for recalls with the U.S. Consumer Product Safety Commission. We found no independent lab test of these adapters.
Frequently asked questions
What is a VoIP adapter?
It's a small box that connects an ordinary home phone to your internet router so the phone can make calls over the internet. You still need phone service, either bundled with the box or from a provider you choose.
Do I need a VoIP adapter for an IP phone or a calling app?
No. A VoIP desk phone or a calling app connects to the provider directly. The adapter is only for analog phones and fax machines.
Is the Obihai OBi200 or Cisco SPA122 still a good buy?
Not new. Poly stopped supporting OBi adapters in 2023, and Google lists the OBi200 and OBi202 as discontinued for Google Voice. Cisco's SPA112 and SPA122 are retired too. A Grandstream HT801 v2 or HT802 v2 covers the same jobs.
Should I choose Ooma or an open adapter like Obihai or Grandstream?
Choose Ooma if you want service that works out of the box and don't mind being tied to one company. Choose an open adapter if you want to pick your own provider and can handle a few settings.
Can a VoIP adapter send faxes?
Often, if both the adapter and the provider support T.38 fax relay. Results vary, so test a few pages before you rely on it.
Will a VoIP phone work during a power outage?
Only if the modem, router and adapter stay powered, for example on a small battery backup, and your internet provider's network is still up.
