What Is Voice Messaging?
Also known as "voicemail," voice messaging lets callers leave messages for subscribers (users) of the system. Voice messaging systems are frequently used in conjunction with PBX systems, mobile phones and residential phone services.
Voice messaging includes several core components. The message collection process is activated when a caller is unable to reach a system user. The message collection application receives data from the phone system indicating which subscriber the caller was attempting to reach. The application plays a greeting then records the message. The greeting may be a standard system greeting or a custom outgoing message recorded by the subscriber.
Once the message has been recorded, the notification component of the voicemail system takes over and lets the subscriber know that a new message is available. This is handled in different ways depending on the type of phone system with which the voice messaging platform is integrated. In most cases, the voicemail system will send a command to the upstream system (PBX, mobile switching platform, etc.), telling it to turn on the message waiting indicator (MWI) for the subscriber's phone. The notification system may also send an email which may include an audio file attachement of the message.
When the subscriber receives the notification they will access the message using one of several methods. Legacy voice messaging systems require the subscribe to call into an application, authenticate using their extension number and password, and listen to their store messages sequentially. More modern systems allow the subscriber to review their messages on their desktop or mobile phone directly using "visual voicemail." If the message was delivered in an email, the subscriber can listen using their computer as well.
Once the message(s) have been reviewed, the messaging system sends another command to the upstream phone system, instructing it to turn off the message waiting indictator and/or decrease the message count.
Advanced voice messaging is a key component of "unified messaging" platforms -- systems that combine multiple messaging formats into a single point of access for the subscriber. In a unified messaging system, the inbox will contains voice, email, fax and sometimes text (IM and/or SMS) messages. Unified messaging is frequently bundled into an even more comprehensive platform called Unified Communications or UC.
Key Facts & Features
All voice messaging systems are able to record messages, notfiy subscribers of waiting messages and provide secured access to those messages. Voice messaging has become a standard feature on most phone systems, but most vendors still sell it as an add-on or "adjunct" product.
Advanced voice messaging systems can forward messages directly to subscribers as an email. In some cases the subscriber will still need to delete old messages from the voice messaging system. More advanced, unified systems will synchronize message status automatically.
There are several standards for integrating voice messaging systems with PBXs and other telephony platforms. These include simple "in-band" integrations that use touch-tones and more complex "out-of-band" integrations that use various technolgies. One of the more common standards is "System Message Desk Interface" or SMDI.
If properly implemented, voice messaging can increase productivity and enhance customer service.
Asterisk As A Voice Messaging System
Asterisk's standard voicemail components make it trivial to assemble a world class messaging platform. With multiple message store options and support for multiple integration techniques, replacing an aging enterprise voicemail system with an Asterisk server is simple.
For information on Asterisk-based voice messaging products, see the AsteriskExchange.