What Does a Modem Do?

The main step to going online

A modem is a device that receives an analog signal from your Internet Service Provider (ISP) and then converts it into a digital signal your devices can understand and vice versa. Effectively, it's a communication device so your computer and other devices can send and receive data over the internet through it. 

Modem is short for modulator demodulator.

What Is the Main Function of a Modem?

A modem is your entrance to the internet. Because it translates the data for you, it's a form of interpreter converting the signal from your ISP to a universal one your computer and other devices can understand. That applies whether you use a cable provider such as Comcast, fiber optics from FIOS, satellite such as Direct TV, or a DSL or dial-up phone connection. 

Typically, your ISP provides you with a modem compatible with the company's services. 

What Does a Modem Look Like?

A modem is usually a small box - either black or white-colored - with a series of lights and port connections on it. 

The lights are usually along the front of the device so you can see what's going on. One light indicates the modem is receiving power, while another tends to demonstrate you're receiving data from your ISP. The modem may also display other lights to show if there are any issues with the service. To know how these work, you need to consult your ISP modem's manual as each reacts differently. 

On the back are ports such as a power socket and Ethernet connection, so you can plug the modem directly into your computer or into a router, depending on your network setup. 

Do You Need a Router If You Have a Modem? 

Not necessarily, but most households have both modems and routers nowadays. That's because while you can plug your modem directly into your computer, it's not possible to use it with multiple devices unless it's a Wi-Fi modem or you've connected the modem to a router. Most households need to use a router alongside a modem to be able to use their internet connection across different devices at the same time. 

If you solely own a computer, you don't need a router as you can connect the modem directly to your PC or Mac. However, router security is generally much better than anything a modem can provide alone.

What Is the Difference Between a Wi-Fi Router and a Modem?

A modem helps translate data between your ISP and your computer. The Wi-Fi router transmits data across all the devices within your network. Essentially, a Wi-Fi router is like a hose connected to the modem's tap. While a tap will deliver water to the same source, a hose can extend where the water reaches.

We have a more detailed look at how modems and routers differ and what it means for you.

Why Do I Need a Modem for Wi-Fi?

If you want a Wi-Fi network to connect your different devices but not access the internet, you don't need a modem. However, it's very likely you also want to connect to the internet with all these devices. If so, you need a modem so your home network can connect with the broader network set up by your ISP so you can browse the internet from home. 

  • What does rebooting a modem do?

    Often, rebooting a modem can solve sudden internet issues. If you experience slowdown or connection problems out-of-the-blue, rebooting your modem is usually one of the first troubleshooting steps.

  • What is the NAT function on modem or router?

    NAT (network address translation) is represented by different NAT types, such as Open or Moderate. A NAT type describes how easy or difficult it is for your device to connect to external public servers. With an Open NAT type, when playing games, for example, you'll be able to connect to the most games possible and have the best chance at having a good connection to those games.

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