Asterisk Technology

| Sunday, January 17, 2010


  • What is Asterisk? And How it works?
  • Features Provided by Standard Asterisk
  • How to configure Asterisk?
  • Various Flavors of Asterisk
  • Why asterisk is batter then other PBX Solutions Available?
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What is Asterisk?

Asterisk is basically a Soft PBX solution created by Mark Spencer in year 1999. Since then it’s the most popular Open Source VoIP PBX solution across the Globe.

Using Asterisk you can do calling vai. Soft phones configured on your PC’s, Laptop or on you Mobile, Analog Phones or IP Phones. Asterisk can work over any type of service line like Old PSTN telephony, Digital PRI E1/T1 telephony or Voice Over IP telephony.

The best part of Asterisk is you can customize Asterisk & make you own telephony solutions on top or it as per your business needs. Asterisk do support multiple platform like, Linix, NetBSD, OpenBSD, Mac OSX, & Solaris.

Features Provided by Asterisk

Well Asterisk do provide many features available in propriety PBX Systems like:

* Voice Mail
* Conference Calling
* Interactive Voice Response
* Automatic Call Distribution

Apart form the standard features uses can create their own features by writing dial plan script in Several Asterisk own extension language.

Asterisk provides an Hybrid telephony architecture by supporting MIX of traditional (PSTN, PRI, T1, E1) & VoIP telephony services. Asterisk allows the users to deploy totally new Asterisk based system, or gradually migrate existing system to new technologies.

For connecting the traditional PSTN Lines to Asterisk Server we have to use PCI Telephony Cards made by Digium or some other companies also.

We can connect Analog PSTN lines to Asterisk box via FXO Cannel Bank also. And to connect PRI E1/T1 interface we can use either PRI Box Packed Gateway or TDM based PCI Cards.

Asterisk support wide range of video and voice over IP Protocols including SIP, MGCP and H232.

Deployer can write their own code over asterisk by implementing Asterisk Gateway Interface (AGI) program using any programming language capable of communicating via Standard stream language of by network TCP sockets.

Asterisk provides all features supported by traditional PBX, it also offer the advanced features that are often associated with large, high end propriety PBX’s.

Call Features provided by Asterisk

Please refer following link

How to configure Asterisk?

You can configure asterisk by yourself or you can take help form some Asterisk consultant. Please refer the following portals for further information:


Various Flavors of Asterisk Available

There are various Flavors of Asterisk available in market few of them are:

- Druid
- Elastix
- TrixBox

Druid OES

Druid OES is an Open Source Unified Communication Platform that brings together IP-PBX, IM, Faxing and Collaboration functionality. Druid functionality is based on various open source projects like Asterisk, Dojo Toolkit, PostFix, HylaFAX, Jabberd2 and Davecot. All these packages offer various functionality combined to make Druid Platform.

Druid provides a full flash Asterisk GUI Interface, hence easy to configure Asterisk. Major advantageous points of Druid are:

1)Auto Provisioning of IP-Phones

Druid Provides full auto-provisioning to IP Phones. It means we just have to plug IP Phone to the network and it Start working without providing the MAC address.

Mainly Auto provisioning available for Polycom, Grandstream, Astra, Linksys, Snom, Cisco and Mitel.

2)External Application Integration

Druid had a SOAP API, which can be used to integrate third party application for mobile phones, desktop etc..

3)FAX to Desktop

Druid provides FAX to desktop features which allows users to send FAX via Desktop PC also and receive the FAX in PDF format over their email ID.

Hardware Support for Druid

Druid is highly supportive to various hardware from various companies like: Sangoma, Digium, Rhino Equipment, Redphone and Xorcom.



Elastix is an open source Unified Communication Server that brings together IP PBX, email, IM, Faxing and collaboration Functionality. It provides web interface and includes capabilities such as Call Center Software with predictive dialing.

Supported Telephony Hardware for Elastix

Elastix provides drivers for many Hardware manufactures including: OpenVOX, Digium, Sangoma, Rhino Equipment, Xorcom and Yeastar.

Elastix mainly supports various phone brands that do support SIP and IAX protocols.


Why Asterisk is batter then other Box-Pack Solutions available in market?

Asterisk provides integration with various existing applications like Custom CRM Integration, Call Center Integration and Automated Calling. System capable of sending thousands of phone calls per minute.

Major advantages of using Asterisk over standard PBX in market like: CISCO, Avaya, Alcatel, Nortel and others are..

1) Asterisk provides easy integration with existing software applications like (CRM, ERP, Call Center Software, POS, PMS ect..)

2) There in no need to purchase license to expand telephony network via Asterisk

3) Reduce the management cost

4) Provides easy integration help to bring SIP, TDM, IAX on single platform.

5) Asterisk can create various flexible Hybrid telephony solutions including Analog PSTN, PRI and VoIP Trunks lines managing through single Asterisk Server.

6) Easily customized as per organizational requirements

7) Regularly upgraded over internet

8) Asterisk can also integrate with existing Analog or Digital PBX system.

Ashvini Gaur
LinkedIN Connect

How FXO and FXS Works?

| Monday, December 14, 2009

Foreign eXchange Subscriber (FXS) and Foreign eXchange Office (FXO) are the names of the two most common interfaces (ports or plugs) found in analog telephony architecture.

FXO and FXS in General Terms

FXS - Foreign eXchange Subscriber interface (the plug on the wall) delivers POTS service from the local phone company’s Central Office (CO) and must be connected to subscriber equipment (telephones, modems, and fax machines).
In other words an FXS is an interface points to the subscriber end. An FXS interface provides the following primary services to a subscriber device:

Dial Tone
Battery Current
Ring Voltage

FXO - Foreign eXchange Office interface (the plug on the phone) receives POTS service, typically from a Central Office of the Public Switched Telephone Network (PSTN). In other words an FXO interface points to the Telco office. An FXO interface provides the following primary service to the Telco network device:
on-hook/off-hook indication (loop closure)

** If you connect an FXS device to another FXS device, the connection will not work. Likewise, if you connect an FXO device to another FXO it will not work. So, for example, you can NOT plug a standard analog telephone (FXO) directly into a standard analog telephone (FXO) and talk phone-to-phone.

FXO and FXS Devices in PBX / IP-PBX

We connect the FXO interface on a phone to the FXS port supplied by a PBX, multiplexer, or Voice-over-IP gateway or router.

A PBX provides both FXS and FXO interfaces:

FXS - When you connect a PBX to analog phones, you plug phone cables into FXS ports on the PBX. The FXS ports on the PBX provide POTS service, including battery current, ring voltage, and dial tone to the phones.

FXO - When you connect a PBX to the Telco Central Office, you plug the (FXS) lines from the phone company into FXO ports on the PBX. The FXO ports on the PBX provide onhook/off-hook indication (loop closure) to the local Telco network.
FXS - FXO Call Procedures

An FXS device initiates a call by presenting ring voltage over the line to the
attached FXO device. (FXS devices cannot pass dialed digits.)

An FXS device receives a call by . . .
1) Detecting the line has been seized (the attached telephone–FXO device–has gone off hook)
2) Receiving Dual-Tone Multi-Frequency (DTMF) digits indicating how the call should be routed.
Line Power FXS devices supply approximately 50 volts DC power to the line. During an emergency, FXO devices can use FXS line voltage for power in order to remain operable in the event of a local electrical power failure.

An FXO device initiates a call by . . .
1) Going off-hook to seize the telephone line.
2) Dialing the Dual-Tone Multi-Frequency (DTMF) digits, which identify the destination to be called

An FXO device receives a call by . . .
1) Detecting the ring voltage supplied by the FXS device (VoIP Gateway, PBX, etc.).
2) Going off-hook to answer the call.

FXO and FXS in Hybrid Telephony Architecture -->>

Ashvini Gaur
LinkedIn Connect

Advantages of using VOIP

| Thursday, March 19, 2009

VOIP is a wonderful technology, which lets user to make voice calls utilizing broadband Internet connection rather than utilizing regular phone line. Some VOIP services may permit user to call anybody he wants who has list of telephone numbers including mobile, international and long distance numbers. Some VOIP services work only over your computer and some VoIP services allow user to utilize a traditional phone that is connected with a VOIP adapter. VOIP services are great medium to convert any person’s voice into a digital signal, which travels over the Internet.

The great advantage of VOIP services is you are provided with many interesting features and great services, which are not obtainable with a conventional phone. VOIP is highly developed technology that has surpassed the mobile and telephone companies. Its popularity is increasing day by day because of its best network coverage. It is an amazing invention created telecommunication completely in a new mode by utilizing Internet. It is an abbreviated form of Voice over Internet protocol.

Let us have a look at its key features. Its key features have attracted many people towards itself. You can call easily and in cheap prices with VOIP technology. It becomes easy to make local, international and long distance calls just by utilizing high-speed broadband net connection. The important benefit is the ability to direct the incoming calls to the VOIP service. Using VOIP system, one can even obtain the detail information of incoming calls from any of the computer having Internet. Another great advantage is user will never miss any of his important call though he is out of town as it follows him wherever he goes. It helped in cost reduction because we can make a call in cheap rates. As a result, the rate of monthly telephone bills is very less which is advantageous economically.