ABC of the IP PBX

Have you ever thought that what actually is an IP PBX and how does it transfer the calls to the target phone number to be contacted? Or how does it locate the device to be contacted? Here, I have all the answers to the questions that are popping up in your mind and making you think that this is too technical, not for a non-technical person like you and me. Basically, all the calling taking place through VOIP network follows client-server approach. This means that IP-PBX is a server and all the phones; whether hard phones, soft phones or analog phones with an ATA (Analog Telephone Adapter); that connect to this server for calling purpose are the clients.

IP PBX Server and client SIP phones

The IP PBX server works as all other servers do. It sits at the center of the IP network and hears the client phones. As soon as a new phone logs-in by entering use
ame and password to avail the VOIP telephony services; it gets listed as the client member of the network and thus it can make or receive calls through the IP PBX server. These clients, also called SIP clients can anytime ask the IP PBX to establish the connection to the destinatio
SIP phone number. Each time a call is to be connected, the server asks the use
ame and password of the SIP client. If the password or use
ame is not correct, the call cannot be made.

The IP PBX server has a directory of all SIP phone numbers along with their corresponding SIP address entries and thus each time, one SIP phone wants to establish a connection with another SIP phone that is already registered on the network by dialing the phone number, the IP PBX looks up the SIP address, tracks its location and connects to that phone. The IP PBX is able to connect a call i.e. internal to the VOIP network or route an exte
al call via either a VOIP gateway or a VOIP service provider. The VOIP gateway is a device that connects different types of networks. If the gateway is connected to an analog network, then it acts as an ATA (Analog Telephone Adapter) that digitizes the analog data and sends it via the VOIP network. Thus, an IP PBX can be used to switch calls between a VOIP user and a traditional telephone user or between two traditional phone users in the same manner that the old PBX switches the calls.

How IP PBX is an intelligent server?

IP PBX server not only transfers the VOIP calls but it is also used by its clients for transferring data. The IP PBX uses the same line for transferring both voice and data. It gives the first priority to transfer the data packets and in the intermittent gaps between the voices, it sends the data accessed via internet. For an example, when you speak “Hello! How are you?” on one SIP business phone, first each alphabet is digitized or converted to the language that computers and servers understand i.e. in bits and bytes and thus a stream of bits is generated, which is then packetized i.e. some given number of bits are collected to form packets. Then these packets are transferred via VOIP network. And, after the word “Hello” as per the above example is transferred, in the gap between the end of this word and the start of the next word, the internet access data is sent. Thus, the transfer line of both voice and data is a converged one. This saves the network bandwidth to a great extent.