At this week’s Consumer Electronics Show in Las Vegas, at least three companies are introducing cordless phones that use a Wi-Fi connection to make calls over eBay’s Skype Internet phone service (a technology sometimes known as “VoIP,” for voice-over-Internet protocol).

Wireless-equipment firm Netgear and appliance makers Panasonic and Phillips all said they will bring out phones that add some measure of mobility to the experience of making a phone call over the Internet -- an activity that has, for the most part, required users to wear a headset attached to a computer with an Internet connection. Panasonic said it would also introduce a Wi-Fi phone that works with Vonage, the leading Internet telephony company.

I’ve been using a similar phone with Vonage’s network, the UTStarcom F1000, which Vonage itself is selling for $79.99 (after a $50 rebate) plus $14.99 per month for the company’s Basic 500 Plan. This small, lightweight gizmo is a lot of fun if you live and work in buildings that have Wi-Fi networks. It’s also an easy way to try out the wonders of Vonage. But even though the F1000 looks like a little cell phone, it’s not really practical as a replacement for that device.

With its stubby little antenna, green and red “phone” buttons, and square one-inch monochrome dot-matrix screen, the F1000 resembles a 1999-era cell phone, except that it can’t transmit more than a few dozen meters. Fortunately, it doesn’t need to. Like a wireless laptop, this phone uses 802.11 Wi-Fi networking technology. When you place a call, the F1000 digitizes your voice into data packets that are sent to the nearest Wi-Fi base station.

The base station then sends the packets over the Internet to Vonage, which turns the packets back into the sound of your voice and completes the phone call. Because it doesn’t need as much transmission power as an ordinary cell phone, the F1000 has a battery life of two or three days, depending on how often you use it.

As a phone, the F1000 has some great features but an equal number are missing. You can use it to call any phone in the world, but it only works if you are within range of a friendly wireless network. The voice quality is a little compressed but not annoyingly so. The phone’s caller-ID feature displays the caller’s name or phone number, but not both. You can load the phone’s 200-number memory from the call log, but not from your PC. There’s a microjack to plug in a headset, but no built-in speakerphone. The phone charges with a standard mini-USB connector, but charging takes hours.