Get started with SIP telephony
SIP telephony works best with real hardware phones, and there are very competent phones for a low price for sale.
But to get started with SIP telephony, you can start experimenting with a software phone for for example an Android phone.
Note that there is a difference in quality compared to a real hardware phone, but to get started it may be a good alternative.
Start with regestering a free SIP account at a SIP supplier, a good choice may be sip2sip.info.
Next, install a sip application on your Android phone or iPhone, for example antisip, and configure the app with your sip account.
To be able to test calling with SIP telephony, one possibility is to use another sip account and another Android phone.
You could also call the test addresses that some sip SIP operators have.
For sip2sip.info there is an echo address: firstname.lastname@example.org
There is also an address with music: email@example.com
When you have come this far, and decided to use SIP telephony it is time to buy at least one hardware phone.
A hardware phone is a relatively low one-time cost, there are no call fees to call with sip telephony.
For anyone already having an Internet connection the call cost is zero since the internet connection is already paid for,
and that cost whether or not SIP telephony is used.
There is currently a number of free sip services, and even if we can not guarantee that will always remain so
there is lots of evidence the cost will be zero or close to zero.
To maintain a sip server is cheap per user since the handling does not take much resorces from the server.
One possibility is the phone Yealink T21P E2.
It can for example be bought at amazon.com
for less than 60 USD.
When the phone has been bought it needs to be configured, that is described in detail here.
It is that easy to start with free and open telephony!