 around 15 years ago while I was just studying there was a lot of hub hub about call centers that is a place where bulk calls are entertained so I would just think about it and then move forward because I didn't have the time nor the energy to look into the technical aspects of a call center but it's such an important phenomenon and one of the most vibrant activities generated from the next generation architecture that we need to understand how call centers evolved and what is the responsibility of the computer telephony integration in this regard so we look at this in due course. So a call center is essentially an infrastructure an IT infrastructure that integrates web email and voice with customer relationship management that is our database to handle a lot of calls. It allows the companies to reach out to existing and potentially new customers so for a large number of incoming calls so many operators handle these calls so there is a automated call routing configuration mechanism. So technology found immense hype and gusto in call centers because two very important aspects of call centers were inspired from intelligent network IN design. The first one is automatic call distribution and the other one is private branch of branch exchanges. So call center is a very interesting phenomenon where the computers and the telephony actually merge. So computer telephony integration is a smart move from not so traditional but it's almost a past phenomenon where we just had the automatic call distribution on certain branch exchange using proprietary routing engines. These proprietary routing engines would make routing decisions through the instruction set or through the rules provided to them one time in a given scenario. But in its advanced form the computer telephony integration incorporates complete databases of customers and interacts live with the customer data to have a better calling and call experience both for an arbitrary customer and the call center representative. Using CTI we can think about integrating multiple call centers across the globe into a logically centralized location. So this actually means that we have to combine the call routing decisions into a central place because the calls would now be routed to different parts of the world transcending across the nation state boundaries which would stay transparent to the caller. This is how typical computer telephone integration in a call center would look like. So if you look at the more traditional view we call it the first party call control. We could think about making a call as a calling party or receiving a call as a call party on a computer that emulates the functioning of the handset the dial pad and the ring tone on a computer similar to how a telephone behaves. On the right hand side we have a complete architecture of a call center involving different call center operators or the agents which are connected to the CTI server which is actually taking a live customer database to reroute the incoming calls on TDM trunks using automatic call distribution facility. So this apparently complex interaction can be ironed out. It could be understood through a certain example. It's very mechanical but we are going to look at the sequence diagram just a couple of slides ahead. Now just quickly understand how a call is made. So at the automatic call distribution facility on TDM trunk a call arrives. ACD places it in a queue depending upon the direct dial-in service or the dial number identification service. Then ACD informs the CTI mechanism that the call has been made. CTI now starts looking up the database using the DNIS or the CLI. If a certain corresponding customer ID is discovered, CTI server instructs ACD to place the call in a specific queue of a certain agent. The ACD places the call in the queue and acknowledges the CTI server of the activity. The agent now is available on his PC or IP telephone and this message of the agent availability sent to the CTI server. CTI server immediately looks up in the customer database and passes the relevant customer related information to the agent using a pop-up screen on the on the computer. So agent gets in conversation with the caller and once the customer query or the client interaction is done, it could be wrapped up or more data could be queried from the customer database by bringing the customer on hold and then resuming the call. So this is how we think about the call center interaction with a certain customer through different agents. This is essentially the summary of the example which I just shared with you in the form of a sequence diagram.