In the current mobile network CLI (Call line Identifier) is one of those common but important services that mobile providers will provide to their subscribers. Correct delivery of the calling party’s number is very important to mobile operators and carriers. However in the reality a lot of reasons can cause the CLI delivered failed or a wrong number is delivered instead of the real calling number. Failed CLI delivery means poor services of a mobile provider and economic loss. To provide an accurate CLI delivery, mobile operators and carriers need an advanced tool that can test CLI delivery whenever they want. This is the reason why we need a flexible system to detect CLIs.Usually, each mobile operators will hold a batch of routes from differet suppliers. By this CLI detecting system, they can easily tell which route provides the best CLI service and which doesn't. And further imporvments will be done according to the testing results of the system.

The goal of this thesis is to design and implement a prototype of CLI detecting system. After comparing among several suitable devices,
Symbian is chose as the platform of this system.One great contribution of the thesis project is providing a detailed but simple programming guide of Symbian. After going through many related Sybmian programming books, API and real coding work, this guide was made. The guide will be very helpful for future developers who may continue on improving this system or who want to start programming on Symbian platform.

In the practical work part of the thesis, it will give a demonstration on how this CLI detecting system works and shows some testing results that got from this system. From these testing results a further step investigation has been done and the real reason that causes the
failed CLI delivery was finally found.