Voice Over Intranet Based Private Branch Exchange System Design

Sandeep Sonaskar Research Scholar, Department of Electronics Engineering,

G.H.Raisoni College of Engineering Nagpur, India

sandeepsonskar@gmail.com

Shubhangi Giripunje Professor Department of Electronics Engineering,

G.H.Raisoni College of Engineering Nagpur, India

shubha_giripunje@yahoo.com

Abstract— The major drawback of the Electronics Private Branch Exchange System is that it required extra wiring for the installation. This system is not flexible in the manner of moving the extension of a particular user to different location. It neither has the caller ID facility nor the “voicemail” facility when user is offline. To find the solution to overcome the problem the Voice over Internet Protocol (VoIP) technology is used. This research includes an architectural solution to integrate the voice over IP (VoIP) services in Infrastructure management network of an organization as a Private Branch Exchange (PBX) instead of EAPBX system. Voice over Internet Protocol (VoIP) is a technology for voice communication that uses the ubiquity of IP-based networks to deploy VoIP client devices such as desktop IP phones called Session Initiation Protocol (SIP) phone or soft phone, in an increasing number of businesses and homes around the world because IP is the protocol connecting almost all devices. Voice over IP (VoIP) uses the Internet Protocol (IP) to transmit voice as packets over an IP based network.

Keywords— VoIP, PBX, trixbox, USB Handset

I. INTRODUCTION VoIP that is Voice over Internet Protocol deals with the

conversion of analog audio signals like when we talk on phone into the digital data that can be transmitted over the internet by using internet protocol. VoIP turns the standard internet connection into the phone calls. Many organizations uses Electronic Private Branch Exchange System for the communication using extension numbers assigned to the users. It utilises the man power and extra wiring for the installation as well as it doesn’t support the advance facilities like call waiting, voicemail, caller ID etc. Its main disadvantage is that the change of extension is very difficult task. The Private Branch Exchange run on VoIP telephony provides the organization the sophisticated installation and configuration of the user extensions. This technology reduces the cost and the time of the installation and configuration, it doesn’t require that much manpower as EPBX system. The project aim is the implementation of the VoIP telephony system software and its configuration. The base is the operating system called “trixbox” which is Linux based VoIP PBX server operating system. These operating systems consist of the telephony package called “Asterisk”. This package consists of several features such as Voicemail, Call Waiting, Caller ID, Conference, Call Hold, Call Transfer etc. Asterisk supports audio protocols such as SIP which is Session Initiation Protocol used for the audio communication. The VoIP PBX system for the organization

use the backbone of Local Area Network on which the extensions were configured using computer system. The “trixbox” server is the Linux based and the clients were the windows based or Linux based using the “Softphone” for the communication. Instead of Softphones the VoIP telephone devices such as USB handset and Hardphones can be used.

II. PBX SYSTEM The Private Branch eXchange (PBX), which provides

telephony services for the telephone system. Therefore, there is a requirement for a PBX to

effectively manage calls and ensure that they go via the most cost effective and reliable routes in order to keep the company communicating internally between departments and employees.

In its basic form, a PBX is the interface between the public telephone network and the private network within the company. This costs little more than the maintenance of the PBX and internal cabling, and there are no line rentals or other call charges being paid to the telecommunications provider. The PBX then handles all of the routing in and out of the company using the lines effectively. The PBX also handles calls within the company so that a call from one internal phone to another does not have to go out onto the phone circuits and back in.

As PBXs became more common, businesses and their employees required more features and functionality such as voicemail, call parking, call transfers, music on-hold, IVR menus, least-cost routing, and an Automatic Call Distributor (ACD) in order to provide for calling groups. With the increase in demand for communications in all aspects of a business, the features required in a phone system become more complex and more expensive. If modern companies had to rely on the telecommunications provider for all these features, the cost of communication could become prohibitively high.

The traditional PBX system is usually a large box full of mechanical switches and relays mounted on a wall in 'the phone room'. When a company's requirement changes, they generally contact their PBX provider who will charge varying rates to make hardware and configuration changes to fit the new requirements. With PBXs being very complicated and each differing from the others greatly, it can take a considerable level of training and experience to provide the support for a busy PBX system.

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Fig. 1 A PBX System

A VoIP PBX system combines the features of a

traditional PBX system with VoIP functionality. The VoIP system functionality is same as the way the PBX communicates with the phones. It includes the ability to have remote extensions. No wiring cost as we use the already installed Local Area Network for the system.

The Asterisk PBX system is a full hybrid system combining numerous types of connections to the public telephone network as well as VoIP functionality including

• Remote extensions using either SIP-compliant phones, or Soft Phones

• Simple Web based Configuration • Use of industry-standard SIP-compliant phones

Fig. 2 Asterisk PBX System

A. Asterisk Asterisk is open source PBX software which runs on

Linux platform. It consists of the SIP protocol along with all the features which is required for the PBX system. The feature includes call forwarding, queuing, call waiting, call transfer and most useful voicemail service.

B. Trixbox The “trixbox” system is made up of a number of

components each of which is released under an open-source license. In this paper the Trixbox CE V 2.0.8.12 is used. Trixbox is the open source IP telephony software consists of the Asterisk PBX package. The main feature of the operating system is that the sophisticated installation & configuration of the system.

III. BEFORE BEGIN • System requirement • Extensions • Connectivity • VoIP • Telephones

i. Hardphone ii. Softphone

i) System Requirement The minimum configuration of the system is Intel

Pentium processor 2.4 GHz, 865 Motherboard, 1 GB RAM, 160 GB IDE Hard disk, D-link Ethernet card (10/100), CD ROM, Keyboard, Mouse and15” TFT monitor

ii) Extensions The Extension numbers are depending upon the number

of employees. Minimum three digit extension number is used example 101,102 and so on. These numbers are created and configured on the server via web interface. These are easily created and deleted. The client system uses “Softphone” or “Hardphones” which are configured using these extensions. The user gets the extension number as well as password to switch on the phone. The username is displayed on the screen of the phone. While creating the extensions voicemail facility is enabled. While there are many more codecs available, these represent the most common ones that are in use today. G.729 is one of the most preferred codecs especially for remote users

(a) Hardphone One of the advantages of Asterisk PBX is its ability to

use any SIP-compliant telephone device. The type of Hardphone is “USB Handset” which is plug and play device and compatible for all the operating systems. The USB handset looks like a regular land line telephone. It consists of the USB controller, Audio Processing Unit having audio pre and power amplifier for MIC and Speaker & a keypad controller for 4X3 keypad.

Fig.3 Block Diagram of USB handset

This USB handset is the plug and play device means no need to install it in system it is automatically installed when plugged into the USB port of PC. The AVR microcontroller ATmega8 is used as the keypad controller. The block

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diagram shown in figure 3 is the system of USB handset. This handset requires the softphone to run.

(b) Softphone Soft phones, as the name implies are software-based

phones. These are programs that run on our computer and work like a normal extension to our PBX. There are a number of soft phones that work under Windows, Mac OSX, and Linux. The ones below shown in figure 4 is ‘xlite’ run on all of these systems. The softphone is easily configurable phone extensions.

Fig 4 Softphone X-Lite

IV. INSTALLATION OF TRIXBOX SYSTEM Download the Licence copy of Trixbox server operating

system from www.fonality.com which is an ISO image and burn it on CD. At the first time make the system boot form CDROM support from the BIOS setup. Insert the CD and restart the system. We will be presented with a start-up screen with several options shown in Figure 5.

Fig 5 Start-up screen

After that type “linux askmethod” in the boot option. The

installation process begins. Next, we are prompted for a password for the root user. The password must be 6 digit long. The installation process can take a while depending on the specifications of the machine we are using. As shown in figure 6.

Fig.6 Installation Process

When the initial setup is complete, eject the CD and

reboot. To give the static IP address to the server, type “setup” in CLI and configure the NIC as shown in figure 7. Select Network configuration and Run the tool, it will ask for IP address. Enter the IP address with subnet mask and default gateway for example the IP address is 192.168.1.9 and Subnet is 255.255.255.0 and hit OK button.

Fig.7 IP address with subnet mask

After that type “service-network-restart” in the

command line and hit enter. The network connection restarted and the given IP address is assigned to the server and the screen shown in figure 8.

Fig. 8 Network Service

By Restarting the server using instruction “init 6” the

screen after entering Username and Password shows the IP address from which this server is configured. The following lines must be appeared.

Welcome to trixbox For access to the trixbox web GUI use this URL http://192.168.1.9

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For help on trixbox commands we can use from this command shell type help-trixbox.

[root@asterisk1 ~]#

V. ACCESSING THE SERVER IN THE NETWORK By entering the address of trixbox server on the client

machine’s internet browser for example http://192.168.1.9 the screen shows in figure 9.

Fig. 9 Web interface

By clicking “switch” menu it will ask the username and

password to log into admin mode. By default the username is “maint” and password is “password”. Then go to Asterisk free PBX option and we get the screenshot shown in figure 10.

Fig.10 PBX setup page

Here add the new extension by giving the user extension

say “100”, display name say “Alice”, secret as the password for the extension. The port address for the system is “5060” which is the communication port. Leave other fields blank. We can create more than 10,000 extensions depending on the hardware configuration

VI. CONFIGURATION OF SOFTPHONE Now after creating the extensions now we configure the

Softphone on the client/user system which might be windows, Linux or Mac. The software is X-lite which is available on www.counterpath.com. Now by successful installation the extension which is created in server is now configured here by entering the details in SIP proxy setting.

Display name: Alice Extension: 100 Secret: **** Domain: Default SIP Proxy: 192.168.1.9 Once we have all the options set, close the windows and

X-Lite will attempt to connect to our server

Fig. 11 Configured Xlite

If our phone has successfully registered with IP PBX, type in *65 and hit Enter. This will tell Asterisk to read back our current extension. The web interface

After the system properly installed and the extensions are configured the administrator can look after the extension usage. The administrator can see the extensions which are in use and which are not. He also can edit and delete the extensions and give the permission as per the requirement. For that the panel window form the web interface is used. The panel is shown in figure 12.

Fig. 12 Panel

VII. THE VOICEMAIL PROTAL The voicemail is the one of the feature of the system. It

is beneficial when the user is off line on not responding. The voicemail can be sent to any extension and can be access by the user by using voicemail ID and password. The access to voicemail is permitted by the administrator while configuring the user extension. To give the permission go to the PBX panel and select the user extension in setup menu or create the new extension. Here go to the field of

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voicemail and enter the voicemail password by enabling the status of voicemail service in the extensions field.

After the configuration the user can access the voicemail service by simply login to the voicemail service in the web browser. The login screen is shown in the figure 13.

Fig.13 Login Screen

After entering the user extension say “100” for “Alice” and the password provided by the administrator a user could login into its voicemail account to see the voicemail status. Figure 14 shows the user voicemail portal.

Fig.14 Voicemail Portal

VIII. CONCLUSION AND FUTURE WORK This paper describes one solution for a local PBX based

on existing LAN hardware infrastructure. It is a low-cost and modular solution that completely meets its basic function, transporting of voice packets over IP networks. Since most of the processing is performed on a PC it provides a number of additional features.

The main advantage of the system, that it reduces the wiring cost as EAPBX system. The extensions can be easily created, deleted or shifted without disturbing the other communication. The future work would include PBX system based on Wireless Network where the extensions are the wireless pocket device just like mobile phones having almost all the features of mobile phone. Mobile phones required the service provider but this system itself the service provider for the created extensions and most important that this system gives the service free of cost.

ACKNOWLEDGMENT This paper is mainly the result of the author’s activities

when preparing to overcome the drawback of EAPBX system and installing a VoIP PBX system for the small business organization. Author took numerous help from many books, manuals, papers and web pages.

Authors are also thankful to their institute for providing every possible support and resources.

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[2] Md. Zaidul Alam, Saugata Bose, Md. Mhafuzur Rahman, Mohammad Abdullah Al-Mumin “Small Office PBX Using Voice Over Internet Protocol” in ICACT 2007

[3] VOIP How to, http://www.linuxdoc.org/HOWTONVOIP-HOWTO.html.

[4] sipX- VOIP http://www.sipfoundry.org. [5] Asterisk PBX System http://www.trixbox.org [6] Ale Imran, Mohammed A Qadeer “Conferencing, Paging, Voice

Mailing via Asterisk EPBX” in 2009 International Conference on Computer Engineering and Technology.

[7] Ale Imran, Mohammed A Qadeer, M J R Khan “Asterisk VoIP Private Branch Exchange” in IMPACT-2009

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