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Welcome to the Blue Lynx IP Telephony Knowledge Base. Here, we try to list basic information regarding IP Telephony system and some of our partner-products. 

In the event, you are unable to locate a particular answer, please contact our Support Team at This email address is being protected from spambots. You need JavaScript enabled to view it. 

Q. What is VoIP?
A. VOIP is an acronym for Voice over Internet Protocol, or in more common terms phone service over the Internet. If you have a reasonable quality Internet connection you can get phone service delivered through your Internet connection instead of from your local phone company.

Q. What is an IP PBX?
A. PBX (Private Branch Exchange) is a system that connects telephone extensions of a company to outside public telephone network as well as to mobile networks. An IP (Internet Protocol) PBX is a PBX that provides audio, video, and instant messaging communication through the TCP/IP protocol stacks for its internal network and interconnects its internal network with the PSTN (Public Switched Telephone Network) for telephony communication.

Q. What is an IP Phone?
A. IP Phones are the same thing as VoIP Phones or Soft Phones. These are telephones that use VoIP technologies for making calls over an IP Network or the traditional PSTN networks.

Q. What is SIP? 
A. SIP (Session Initiation Protocol) is a signaling communications protocol, widely used for controlling multimedia communication sessions such as voice and video calls over IP networks.

Q. What is IAX?
A. IAX (Inter-Asterisk Exchange) is a communications protocol native to the Asterisk PBX software, and is supported by a few other soft switches, PBX systems, and soft phones. It is used for transporting VoIP telephony sessions between servers and to terminal devices. IAX now most commonly refers to IAX2, the second version of the IAX protocol.

Q. Comparison between SIP and IAX2
A. IAX2 protocol carries both signaling and media on the same port 4569 (by default). SIP signaling port is 5060 (by default), but media goes through other random ports. For IAX2 you only have to make sure port 4569 is clear then the phone calls can be guaranteed, but for SIP, besides port 5060 also other RTP ports need to be guaranteed too for stability of communication. Otherwise you'll encounter no audio or one-way voice problems, especially between different networks.
From the functionality perspective, IAX2 cannot support variety functions like SIP. SIP is the most widely used VoIP protocol so IP phone manufacturers are willing to develop call features based on SIP instead of IAX2.

Q. What is T.38 fax?
A. T.38 is an ITU recommendation for allowing transmission of fax over IP networks in real time.

Q. What is Distinctive Ringtone?
A. Some IP Phones provide different ring tones based on call source (internal or external) and there's text field to enter Alert-Info so that distinctive ring can be used for that destination.

Q. What is DISA?
A. DISA (Direct Inward System Access) is a mechanism available on some PBX’s that permits inbound calls to be answered and immediately presented with system dial tone. The caller is then able to dial a number that the PBX uses to decide how to forward the call. It is like the caller is able to dial twice – first to reach the PBX, then a second time to reach the final destination using the facilities of the PBX.

Q. What is Smart DID?
A. Define patterns to match the numbers you call, then those numbers will be stored into Asterisk database and be associated with the extensions which made the calls. If those numbers call in again, the calls will automatically call on the extensions that associated previously.

Q. What is BLF?
A. BLF (Busy Lamp Field), typically a collection of lights or indicators on a phone that indicate who is talking on other phones connected to the same PBX. Used by a receptionist or secretary to aid in routing incoming calls.

Q. What is FXO lifeline to FXS?
A. FXO lifeline to FXS is a feature that provided by FXOS and 2FXOS modules, the FXO port can allow a PSTN call to ring/call the phone connected to the FXS port on the same module so it serves as a life line in case of power outage. If the mentioned modules are installed then that IP PBX can support this feature.

Q. What is call parking? How does it work?
A. Call parking is a feature of Asterisk that allows a user to put a call on hold at one extension and continue the conversation from any other extensions.

Q. What is Phone Provisioning?
A. Phone provisioning or auto provisioning is an easy and time-saving way to configure IP phones for IP PBXs. With phone provisioning, all user information can be entered via the IP PBX web interface. Required is the MAC address of the IP Phone, the desired extension and the caller ID which is displayed on the called party phone display. The IP Phone receives the configuration via the local network. This offers many advantages, i.e. it is possible to configure phones centralized, which saves a lot of time and money.

Q. How do I configure phone provisioning?
A. First, you need to enable DHCP service on IP PBX, and please make sure there’s no other DHCP service in your subnet. Also please fill in TFTP server address with IP PBX IP address if you don’t use other TFTP server.
Now please configure phone settings, choose manufacturer of the phone and the model, then fill in MAC address and choose an extension number for this phone.
After all done, please attach the IP phones to your switch and power them on then they can be auto provisioned.

Q. What is PnP? How does it work?
A. PnP refers to plug and play of the IP phones, it's another more efficient way of provisioning the IP phones, just enable this feature and power on the IP phones then they can be provisioned.

Q. What does PIN Set do in a dial rule?
A. For example, this rule you configured that can dial international numbers, you don't want everyone to use this dial rule, you can enable PIN Set, so if someone want to call out using this dial rule, he/she needs to enter one of the PIN codes in the PIN Set first, then he/she can call out. Also the PIN number can be traced in the call logs.

Q. What are the advantages of an IP PBX comparing to a legacy PBX?
1. No more phone wiring, it uses you LAN
2. Much easier of installation and management
3. Many more features but much cheaper than a legacy PBX
4. Remote extensions and branch offices, saving your long distance telephone expense
5. Significant cost savings using VoIP providers

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