Google has just made a long-awaited announcement that it will be opening up its Google Voice service to new customers. What's Google Voice? It's a telephone service that provides a number of features to simplify your phone use. It started out as GrandCentral and was acquired by Google two years ago and redesigned over the intervening time. The most significant feature provides you with a free local phone number that becomes your one and only number that you give out to others. When that number is called it rings your various phones, home, cellphone and office, all at once. When you pick up on one of the lines, the others stop ringing. This offers a variety of benefits. Your friends and associates can reach you by dialing the one number rather than having to guess whether you are at home, in the office or out. No more need to hand out numbers and details about where you will be and when. And no further need to check your various voice-mail accounts. Itâ€šs a huge convenience for the both you and the caller. You can choose which phones to ring at any time. Go online to the Google Voice Web site (google.com/voice), sign in, add a new number or select which phones to ring or turn off. If you get a new phone number, there's no need to notify anyone. Just add the new number to the list of phones that you want to ring. When you receive a call you can choose whether to answer it or direct it to e-mail or record it, depending on which key you hit (in the case of choosing to record, a message is played saying the call is being recorded - keeps it all legal). One of the new Google features is that it connects instantly when you pick up the phone; with GrandCentral you needed to hit "1". Once you're on a call you can transfer it. Hit the star key and it will ring your other phones and shifts the call to the line you pick up. That allows you to move a call from your office to your cellphone if you want to leave the office and continue talking. A major new feature is that voice-mail messages left are converted to text and immediately sent to you as an e-mail. The accuracy of the transcription is far from perfect, but it's usually good enough to get the gist of the message. You can also click on a link in the e-mail to play back the message or to return the call. Google Voice also lets you initiate calls from your computer. Click on the number, either in the e-mail message or from your Google contacts, and designate which of your phones you'd like to use. A few seconds later that phone rings and connects you to your call. Calls are free within the 48 states of the contiguous United States and a few cents per minute elsewhere. The calls use VOIP and are generally clear and connect quickly. When you go onto the Google Voice Web site you'll see an inbox, much like Google Mail, listing your incoming calls with the text message and audio file. This list is archived until you delete them. You can designate certain callers, phone numbers and categories not to ring your phone and to take a variety of actions. You can choose that the caller be sent directly to voice-mail or block the call altogether. With the first, the caller hears a ring and is asked to leave a voice-mail. With the latter you can designate that the messages be sent to the spam folder. Or even better for those annoying sales calls, put them on your blocked list and they'll get a message saying that the number they have called is no longer in service. This can be done with, say, all 800 and 866 calls. This is useful in filtering unsolicited sales calls. There's nothing more satisfying than reading the transcription of messages in the spam folder from unsolicited callers wanting you to call back in order to sell you something. I've been using the service, initially as GrandCentral, for nearly three years, and I love it. Google has made a number of improvements and introduced new features, but the general concept remains the same: one number for people to reach you. What are the downsides? It requires you to change your number, notify others, and then put your faith in Google that the number will always work reliably. Google has no call-in support if you do run into a problem. On a couple of occasions it's gone out of service, albeit for less than an hour each time. It also can confuse those you call. They'll see your phone's number rather than your universal number and you may miss text messages. Also be aware that using Google Voice does reduce your privacy. The calls and messages are archived and can be subpoenaed. If you're interested, you can sign up now at google.com/voice. And did I mention, it's totally free! Phil Baker is the author of From Concept to Consumer published by Financial Times Press. He has developed and marketed consumer and computer products for Polaroid, Apple, Seiko and others, holds 30 patents and is an Ernst & Young Entrepreneur of the Year. Phil's blog is blog.philipgbaker.com and his Web site is philipgbaker.com. This column first appeared in the San Diego Transcript and is reprinted with its permission.