Inside A Modem: What Does It Do?

What is a modem?

A modem is a device that connects your home to the internet. Depending on the type of connection you have (cable, satellite, or DSL, 5G, etc.) your modem acts as your home’s connection to your internet service provider (ISP). Because different types of internet connection require different hardware, your modem must be compatible with your internet service. For example, a cable modem is incompatible with a DSL high-speed internet.

A modem can either stand alone or be part of a combined modem and router, called a "gateway ". It's worth mentioning that if you have T-Mobile Home Internet, you have a wireless 5G Gateway device that utilizes the next generation of Wi-Fi technology (Wi-Fi 6) to keep you connected at home.

But if you’re not on a T-Mobile Home Internet plan, you may have a different type of router-modem setup.

What does a modem look like?

Standalone modems are generally small, square black boxes. Not all modems have external antennas, but those that do usually have either two to four antennas. Modems also usually include two to four ethernet ports and one or two USB ports and they usually connect to the wall via a coaxial cable. There should a be series of lights on your modem that indicate that the modem is receiving power and data from your ISP. Some modems also have lights to indicate if there are any other problems affecting service, but you’ll need to look at your modem’s user manual to know what each of its lights mean.

Combination modem and routers, or gateways, are usually tall, thin towers. If they're wired, they have a coaxial cable plug connector, multiple ethernet ports, and usually have at least one USB port.

What does a modem do?

A modem basically acts as your home’s internet hub. Your modem interprets data from your ISP and then converts that data into a signal that your devices can then use to get online. If you have a cable, satellite, or DSL connection , your modem connects to the cable or phone line through a small panel installed on your wall with a coaxial cable. If you have a fiber optic connection, you do not need a modem, but instead need a device called an optical network terminal (ONT).

Where does the router come into play?

Once your modem is wired into to your ISP and plugged into an electrical outlet, there are a couple of different ways you can get internet to your devices. The first is to connect your modem to a Wi-Fi router via an ethernet cable. The router then broadcasts a signal to the rest of your home so that you can connect multiple devices to the internet at once. However, you can also connect devices directly to your modem with an ethernet cable.

Can I use a modem without a router?

Usually, modems and routers are like peanut butter and jelly: they each work much better when used with the other. While you could use them individually, without both, neither is anywhere near as good.

Without a router, you still have access to the internet. However, that access is limited to how many devices you can connect directly to the modem. And since most modems have a limited number of ports and must be connected directly to your ISP through a wall outlet, it would be very difficult to provide internet access to more than a couple of devices at a time. That’s not very convenient in the age of the smart home, where everything from doorbells to dishwashers increasingly require an internet connection.

But without a modem, your router simply creates a closed network within your home or office. This means that the devices can connect to each other, for example, a computer and a printer, though they cannot connect to the internet.

Can I buy my own modem?

Most people are provided a modem through their ISP. The benefit to using a modem provided by an ISP is the fact that you know you’ll be getting the exact right modem for your plan. Since different internet connections require different hardware, some plans require users to rent equipment on a month-to-month basis. For instance, modems are also designed to handle different internet speeds. So you’ll need a different modem for, say, a 1-gigabit plan than you would for a plan that offers speeds of 200 megabits per second (Mbps). You also need a specific modem depending on whether you have cable, DSL, or satellite internet.

However, if your ISP allows you to purchase your own hardware, there are a couple of advantages to doing so. While you may pay more up front, you'll likely save money over the course of a few years. Also, owning a modem that works with multiple ISPs means you have more flexibility to change providers without having to rent and pay deposits on new equipment.

Want an effortless setup?

T-Mobile is America’s fastest growing Home Internet provider. See if it's available in your area now and then find a plan that's right for you.

Once you sign up, a 5G Gateway Device is delivered to your home. No equipment fees. No complicated installation. No wires. It's operated via an app you can download to your phone or computer. Once you download the app, you generally scan a barcode on your 5G Gateway, find a good spot in the room, and get connected in minutes.