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Home PBX System

It's easy to set up your own PBX Telephone System (Private Branch eXchange) at home. In this article I will attempt to clarify some of the tech-speak that the subject matter experts assume you already know and understand.

You start with the Cisco Linksys SPA-9000 which is a SOHO (Small Office - Home Office PBX) System.  It is a very small device, smaller than most routers.  Cisco Linksys usually puts a -NA after its model numbers to designate that they are "unlocked."  This means that you are free to program them at will and they are not locked to a particular phone provider.  So you want the SPA-9000-NA model.

The SPA9000 can support sixteen (16) SIP compatible IP Phones, out-of-the-box.

The Linksys SPA9000-NA marries the rich feature set of high-end PBX telephone systems with the convenience and cost advantages of Voice over IP.

The Linksys SPA9000 has common voice system features such as an auto-attendant, shared line appearances, three way call conferencing, intercom, music on hold, call-forwarding and much more. The SPA9000 opens up access to the benefits of VoIP, including low cost long distance service, telephone number portability, and one network for both voice and data.

The SPA9000 is so easy to configure that a fully working system can be set up in minutes. New Linksys telephones are automatically detected and registered when they are connected to the SPA9000. The SPA9000 has an integrated web server that allow features to be configured using a web browser. The web server has multiple levels of password protected access to user and service level features.

With its integrated router, the SPA9000 can be either connected directly to the internet connection or to another router on your network. The SPA9000 has separate WAN and LAN Ethernet ports. The WAN connection can be connect through DHCP or a fixed IP address. The LAN port can assign IP addresses to IP Phones and computers using NAT and DHCP.

While the SPA9000 will work with any SIP compatible IP Phone, it is the ideal host for Linksys IP Phones, such as the SPA901, SPA921, SPA922, SPA941, SPA942, and SPA962. Powerful configuration capabilities enable the SPA9000 to support a greater set of advanced features with these IP Phones, such as shared line appearances, hunt groups, call transfer, call parking lot, and group paging.

With its two FXS ports, the SPA9000 can support traditional analog devices such as telephones, answering machines, FAX machines, and media adapters.

FXS means Foreign Exchange Station.  This terminology is a carry-over from the old Bell System days.  A Foreign Exchange is a non-Bell System network or connection.  These FXS ports can be used to collect regular telephone sets including cordless phones.

The SPA-9000 connections consist of the two FXS ports, the WAN ethernet port, the LAN ethernet port and power.  This device is quite powerful but don't use it as a router.  Connect your home LAN to the WAN port on the SPA-9000 after configuring it with a laptop on the LAN port.  Enable WAN port web administration so you can make changes to the SPA-9000 over your home LAN.

There are four virtual ports that can be assigned to VoIP accounts from a ITSP (Internet Telephony Service Provider).  You can also assign these ports to a local phone connection but you need to obtain additional equipment to do this.  The companion device is the SPA-400 which consists of four ports that can connect to four regular phone company numbers (PSTN - Public Switched Telephone Network - the "Phone Company")  The SPA-400 also provides Voice Mail for your extensions and a music-on-hold server.



I aldready have a SPA-3102. This device looks almost exactly like the SPA-9000.  It has a ethernet port, one FXS (Foreign Exchange Station) port and one FXO (Foreign Exchange Office) port.  Using the FXS port I can connect an additonal conventional phone to the PBX.  Using the FXO port I can connect my existing home phone line to the PBX.  I can then place outgoing calls and receive incoming calls through the phone company. 

The SPA-3102 will consume one of the SPA-9000 virtual ports to handle the local phone number.  The other three ports are available to be assigned to ITSP accounts.



I have several of these Cisco SPA-504G VoIP phones around the house.  They connect directly to the SPA-9000 PBX over ethernet or you can register them directly to your SIP provider over the internet.  They have 4 lines, a speakerphone, and a 2.5mm jack for a wired headset.  With the SPA-9000 you can communicate over the speaker of another phone without the called party needing to answer.

You can obtain a free phone number from places like Callcentric.  They provide a free VoIP number that allows unlimited inbound and outbound calling between Callcentric users.  They also provide a free DID (Direct Inward Dialing, as in Public Phone Number, POTS, PSTN) so that people can call your VoIP system using a regular phone number.  If you want to place outbound calls they charge a reasonable fee.  For example, unlimited outbound calls to the USA is about $20 per month.  Callcentric charges a small monthly E911 fee if you are located in the USA, even for the free inbound DID.

Now, check out Google Voice.  You can get a free local number from them and assign it to one of your VoIP numbers.  Now when someone calls your Google Voice number it will ring one of your VoIP numbers in the house.  You can also assign your cell number to the Google Voice number so both your VoIP and cell numbers will ring at the same time.  Using the Google Voice web site you can initiate free long distance calls to the USA.  You type the desired long distance number into the web site, Google Voice will call your VoIP number and then call your desired party after you answer and connect you together.

If you want to use the free Google Voice service to make outbound calls directly from your VoIP phone then things get a little more complicated.

Another option is KoTS.  With KoTS you will need that free Callcentric inbound number.  They provide reliable incoming and outgoing calls anywhere; behind NAT, firewall, proxy and even VPN.  There is a $10 per year fee if you want all the features like multiple lines.

Getting a service like KoTS to provide you a seamless integration between Google Voice and your VoIP phones is a challenge because Google is always changing things on their end.  It's not easy for KoTS to keep up with Google's moving target.

Some years ago I cancelled my house phone line.  I use Google Voice now which rings my house and cell at the same time.  Should I have a problem with all my home-grown high tech stuff, at least my cell phone will ring!