Analog Telephone Adapter: How to Use Old Phones with Modern VoIP Systems

When you need to keep using your old landline phone but want to switch to internet calling, an analog telephone adapter, a device that converts analog voice signals into digital data for VoIP networks. Also known as ATA, it’s the bridge between your grandfather’s rotary phone and today’s cloud-based phone systems. You plug your regular phone into the ATA, connect the ATA to your router, and suddenly your analog device works over the internet—no new handset needed.

Most people use an analog telephone adapter, a hardware device that connects standard telephones to VoIP networks via Ethernet or Wi-Fi when they don’t want to replace every phone in the house. It’s common in small offices, homes with multiple landline phones, or for users who prefer the feel of a traditional handset. The adapter handles the conversion between analog signals and digital packets, so your voice travels over your internet connection instead of copper wires. It also manages call signaling using SIP, the same protocol that powers business VoIP systems. That means your ATA talks directly to your VoIP provider, just like a softphone or IP phone would.

But not all ATAs are the same. Some only support one phone line; others handle two or more. Some include built-in firewalls or echo cancellation to improve call quality. If you’re connecting to a provider like Vonage or Ooma, you’ll need one that’s compatible with their settings. And while ATAs are simple to set up, they’re not magic—they depend on your internet connection. Poor Wi-Fi or high latency can make calls choppy, even with the best adapter. That’s why many users pair them with wired Ethernet connections for reliability.

You’ll also find ATAs used in backup systems. If your main VoIP service goes down, some businesses keep an ATA connected to a traditional phone line as a fallback. Others use them to connect fax machines, alarm systems, or medical alert devices that still rely on analog signals. Even though most new phones are digital, there are still millions of analog devices in use—and the ATA keeps them alive.

Behind the scenes, the ATA works with SIP, a signaling protocol used to establish, manage, and terminate VoIP calls. It registers with your provider, sends call requests, and translates audio into packets. This is the same process used by desk phones and apps like Zoom or Skype, just with a physical phone on the other end. If you’ve ever seen a small box with an RJ11 port (for your phone) and an RJ45 port (for your router), that’s your ATA.

There’s no need to buy expensive new equipment if you’re happy with your current phones. The right analog telephone adapter can save you hundreds—and keep your familiar handsets working for years. Below, you’ll find real-world guides on setting up ATAs, troubleshooting common issues, and choosing the right model for your home or small office. Whether you’re connecting a single phone or a whole office system, the right adapter makes the transition simple.