Caratteristiche Asterisk
Asterisk based telephony solutions offer a rich and flexible feature set. Asterisk offers both classical PBX functionality and advanced features, and interoperates with traditional standards-based telephony systems and Voice over IP systems.  Asterisk offers the features one would expect of a large proprietary PBX system such as Voicemail, Conference Bridging, Call Queuing, and Call Detail Records.
Telephony Services:
- Voicemail System 
- Password Protected 
 - Separate Away and Unavailable Messages 
 - Default or Custom Messages 
 - Multiple Mail Folders 
 - Web Interface for Voicemail Checking 
 - E-mail notification of Voicemail 
 - Voicemail Forwarding 
 - Visual Message Waiting Indicator 
 - Message Waiting Stutter Dialtone 
 
 - Auto Attendant 
 - Interactive Voice Response 
 - Overhead Paging 
 - Flexible Extension Logic 
- Multiple Line Extensions 
 - Multi-Layered Access Control 
 - Direct Inward System Access 
 
 - Directory Listing 
 - Conference Bridging 
- Unlimited Conference Rooms 
 - Access Control 
 
 - Call Queuing 
 - ADSI Menu System 
- Support for Advanced Telephony Features 
 - PBX Driven Visual Menu Systems 
 - Visual Notification of Voicemail 
 
 - Call Detail Records 
 - Local Call Agents 
 - Remote Call Agents 
 - Protocol Bridging 
- Provides seamless integration of technologies 
 - Offers a unified set of services to users regardless of connection type 
 - Allows interoperability of VoIP systems 
 
 
Call Features:
- Music on Hold 
 - Music on Transfer 
- Flexible mp3 based system 
 - Volume Control 
 - Random Play 
 - Linear Play 
 
 - Call Waiting 
 - Caller ID 
 - Caller ID Blocking 
 - Caller ID on Call Waiting 
 - Call Forward on Busy 
 - Call Forward on No Answer 
 - Call Forward Variable 
 - Call Transfer 
 - Call Parking 
 - Call Retrieval 
 - Remote Call Pickup 
 - Do Not Disturb 
Scalability:
 - TDMoE 
- Allows Direct Connection of Asterisk PBX 
 - Offers Zero Latency 
 - Uses Commodity Ethernet Hardware 
 
 - Voice over IP 
- Allows for Integration of Physically Separate Installations 
 - Uses commonly deployed data connections 
 - Allows a unified dialplan across multiple offices 
 
 
Voice over IP Interoperability:
Asterisk provides transparent bridging between Voice over IP protocols and traditional telephony equipment.  In addition, Asterisk can transfer calls from one system to another via the Inter Asterisk Exchange protocol.
- Inter-Asterisk Exchange (IAX) 
 - H.323 
 - Session Initiation Protocol (SIP) 
 - Media Gateway Control Protocol (MGCP) 
 
Traditional Telephony Interoperability
- Robbed Bit Signaling Types 
- FXS and FXO 
 - Loopstart 
 - Groundstart 
 - Kewlstart 
 - E&M 
 - E&M Wink 
 - Feature Group D 
 
 - PRI Protocols 
- 4ESS 
 - Lucent 5E 
 - DMS100 
 - National ISDN2 
 - EuroISDN 
 - BRI (ISDN4Linux) 
 
 
Codec Support
- GSM 
 - G.729 (available through purchase of commercial license(s)) 
 - G.723.1 (pass through) 
 - Linear 
 - Mu-Law 
 - A-Law 
 - ADPCM 
 - G.726 
 - ILBC 
 - LPC-10 
 - MP3 (decode only) 
 
Fax Support
- The current state of fax support is incomplete.