Cover Photo by Pawel Czerwinski on Unsplash

In a growing world of digital media, the home phone remains one of the most analogue device in our life. It's powered by POTS, also known as Plain Old Telephone System. The more modern alternative, VoIP or Voice over IP, offers telephony service over your Internet connection. These system can often be cheaper while offering more functionality. Although its commonly found in the enterprise setting, the tech-savvy can also build a similar setup at home. Lets take a look at the components of a typical VoIP system.

SIP Trunk

The first component of a VoIP system that bridges the POTS and the Internet. The first step is to register a phone number at the SIP provider. That number is then associated with a SIP trunk, which will have a connection endpoint on the Internet and a set of authentication credentials. Experimenting with IP telepohny can be relatively cheap, using providers such as Voip.ms or Amazon Connect.

Digital IP PBX

A PBX, also know as private branch exchange, is a phone system which routes calls to different phone extensions. A simple PBX simply routes calls to the first available phone extensions. More complicated implementation can have vocal menu system to route calls to the appropriated extensions. A digital IP PBX is a piece of software that can be installed on any PC hardware, some of them, like FreePBX available for free. They can be connected to traditional phone system (POTS) using SIP trunk. Some advanced SIP provider also have PBX services available.

But I still need a phone?

Unfortunately, normal POTS phones cannot be used natively with a Digital PBX. You can either use an FXS, which bridges the gap between the analog phone and digital PBX, or simply use an IP Phone. There are many FXS on the market, but one of the most simple is the Grandstream HT801. Otherwise, there is an incredible amount of used IP telephony hardware on the market, especially on Ebay. Make sure that telephony hardware allows for SIP connections. Some providers, such as Cisco, have their hardware locked to custom systems. If found used for a good price, Yealink hardware is an excellent value and good compatibility.

POTS Gateway

Although Digital PBX work their best with SIP providers, you can connect a PBX to one (or many) traditional phone lines using a FXO bridge. This emulates the POTS phone as a SIP trunk, so the PBX can receive and send calls on that line. Our best experiences with this type of hardware has been with Yeastar, most notably the Neogate TA810.

Putting all together

The first step in building out our Digital Telephony system is setting up the PBX. In this example, FreePBX is installed on simple PC hardware. In FreePBX, SIP extensions are configured for each of our IP phone device. These SIP extensions include authentication credentials, which are used to setup each device. Note that many IP phones will also provide a web interface to facilitate setup, a definite benefits to entering all that configuration information on a phone keyboard. Each phone is different, but there is a lot of information on the Internet to help you with these steps.

At this point, you should be able to call from one phone extension to another. You can also setup a ring group which acts as a virtual extension that reaches multiple telephone at the same time. You can also experiment with voice mail.

The next step is to get the PBX connected to the traditional phone system (POTS). Chose a SIP provider, rent a DID (phone number) and connect it to your PBX. Good SIP providers will have ample documentation on this step. Once call routing is properly configured, you should be able to receive incoming call from you DID number and call external phone numbers.

If you have an analog phone line and you want to connect it to the PBX, refer to the documentation of your FXS bridge.

Final thoughts

Although more complicated than a simple phone system, VoIP system allow for incredible flexibility and cost saving.

• If you have family in a foreign country, just get a DID directly in that country. Your relatives will be able to call you as if its a local number and you will be able to reach them for great discounts.
• If you have teens that monopolize the phone at all times of the day, just get each their own DID (phone line).
• If you need to forward calls in special circumstances to different numbers, you can setup different call routing rules in a digital PBX.

Note that setting up a PBX is not easy, and it requires maintenance. However, when it comes to learning about digital telephony, nothing beats setting up a small digital call center in your own home.