There is no standard....just like cellular phones!
CDMA, TDMA, GSM, etc., etc., ad nauseum

How to is real easy......

Go to:
http://www.pcsuperstore.com/products/H08985-Linksys-CIT200.html/froogle/
Order the Linksys CIT200 for $80.

Drop its CD into your CDROM drive and install the CIT200 driver software.  
It also installs Skype, which is free.

When it asks, plug in the CIT200 base unit to any USB port on the
computer.  It completes the installation and logs the phone onto the base
onto Skype.  Skype will boot its signup webpage, which costs you nothing,
nada.  Sign up and register your Skype username you choose with the
server in Luxembourg, out of the clutches of the IRS-FBI bureaucrats and
your local tax animals.

Skype automatically logs onto the system as you....almost too easy.

Skype calls to the other 6.5 million Skype users online as I type this is
free, forever, from any wifi hotspot or broadband port on the planet.

To call and be called by landlines from most countries that have
telephones, you sign up for SkypeOut which lets you call OUT from Skype
to telephones and to SkypeIN, which gives you a telephone number the less
fortunate on the planet can call from their old dialup telephones, those
that still have them.  SkypeIn is like Inward WATTS, it seems.  Mine is a
local call from any phone around home.  I'm not sure how far out it works
without the long distance ripoff...??  SkypeOut and SkypeIn are prepaid
from your account you charge up, right over Skype, with your credit card
in $10 increments.  You have 180 days to use up the $10 or they keep it.  
There is NO MONTHLY CHARGE, NO TAXES, NO CELLULAR FUNNY BUSINESS.  Your
Skype interface on your computer screen always shows you your Skype
account balance.  There is no Spyware, adware or other crapware with
Skype.

When you boot your computer, if you have it set to autoload, the CIT200
phone interface boots, connects itself to is little cell on the USB port,
then boots Skype to itself, seamlessly.  As soon as Skype logs onto the
server, you will get your Skype contact list on the wireless handset when
you press the Skype button, in the middle on the bottom.  The phone
controls Skype and its functions as good as the software does with the
mouse, once you learn how....up to 300 meters from the computer, not tied
to it with a headset any more.

If you have any webcam, and you have it connected to your computer, you
may click the MY VIDEO button on Skype on the computer, even if you're
using the wireless phone.  The party on the other end now sees your
webcam picture, that dark outline because you are too stupid to turn a
light on what the cam is point at, on HIS Skype interface.  If both of
you have the simplest of webcams, both of you can see the other and your
own picture on Skype....full duplex color video.  I fixed a TV that had a
bad capacitor in Russia through a Skype-to-Skype webcam chat not long
ago, on the other side of the planet.  Way cool...(c;

Cellphone companies must be pissed......
$80....just ONCE!
You don't even need the phone if you have the simplest of microphones and
speakers on your PC.  Skype has software to eliminate echos speakers
create!