Voicemail (also known as voice-mail, VMS, or message bank) is a centralized system of stored telephone messages that can be retrieved by the recipient at a later time. The term is also used more broadly to denote any system of conveying a stored telecommunications voice message, including using an answering machine. Most cell phones have voicemail as a basic feature, and many land line phones and corporate PBXs have their own voicemail options.
Features
Voicemail systems are designed to convey a recorded audio message to a recipient. To do so they contain a user interface to select, play, and manage messages; a delivery method to either play or otherwise deliver the message; and a notification ability to inform the user of a waiting message. Most systems use phone-networks, either cellular or land-line based, as the conduit for all of these functions. Some systems may use multiple telecommunications methods, permitting recipients and callers to retrieve or leave messages through multiple methods.
Simple voicemail functions as a remote answering machine using a touch-tone as the user interface. More complicated systems may use other input devices such as voice or a computer interface. Simpler voicemail systems may play the audio message through the phone, while more advanced systems may have alternative delivery methods, including email or text message delivery, message transfer and forwarding options, and multiple mailboxes.
Notification methods also vary based on the voicemail system. Simple systems may not provide active notification at all, instead requiring the recipient to check with the system, while others may provide an indication that messages are waiting. Almost all modern voicemail systems use digital storage and are typically stored on computer storage devices.
By the year 2000, voicemail had become a ubiquitous feature on phone systems serving companies, cellular and residential subscribers. Cellular and residential voicemail continue today in their previous form, primarily simple telephone answering. Email became the prevalent messaging system, email servers and software became quite reliable, and virtually all office workers were equipped with multimedia desktop PCs.
Instant messaging in voice: The next development in messaging was in making text messaging real-time, rather than just asynchronous store-and-forward delivery into a mailbox. It started with Internet service provider America Online (AOL) as a public Internet-based free text "chat" service for consumers, but soon was being used by business people as well. It introduced the concept of Internet Protocol "presence management" or being able to detect device connectivity to the Internet and contact recipient "availability" status to exchange real-time messages, as well as personalized "Buddy list" directories to allow only people you knew to find out your status and initiate a real-time text messaging exchange with you. Presence and Instant Messaging has since evolved into more than short text messages, but now can include the exchange of data files (documents, pictures) and the escalation of the contact into a voice conversational connection.
Mobile devices
The increase in wireless mobility, originally through cellular services and today through IP-based Wi-Fi, was also a driver for messaging convergence with mobile telephony. Today it is not only fostering the use of speech user interfaces for message management, but increasing the demand for retrieval of voice messages integrated with email. It also enables people to reply to both voice and email messages in voice rather than text. New services, such as GotVoice, SpinVox and YouMail, are helping to blur the boundaries between voicemail and text by delivering voicemails to mobile phones as SMS text messages.
Unified messaging with VoIP
Corporate voicemail did not change much until the advent of Voice over IP (VoIP- voice being transmitted over the internet) and the development of IP telephony applications to replace legacy PBX telephony (called TDM technologies). IP (Internet Protocol) telephony changed the style and technology of PBXs and the way voicemail systems integrated with them. This, in turn, facilitated a new generation of Unified Messaging, which is now likely to catch on widely. The flexibility, manageability, lower costs, reliability, speed, and user convenience for messaging convergence is now possible where it wasn't before. This might include intra- and inter-enterprise contacts, mobile contacts, proactive application information delivery, and customer contact applications.
The corporate IP telephony-based voicemail CPE market is served by several vendors including Avaya, Cisco systems, Adomo, Interactive Intelligence, Nortel, Mitel, 3Com, and AVST. Their marketing strategy will have to address the need to support a variety of legacy PBXs as well as new Voice over IP as enterprises migrate towards converging IP-based telecommunications. A similar situation exists for the carrier market for voicemail servers, currently dominated by Comverse Technology, with some share still held by Lucent Technologies.
VoIP telephony enables centralized, shared servers, with remote administration and usage management for corporate (enterprise) customers. In the past, carriers lost this business because it was far too expensive and inflexible to have remote managed facilities by the phone company. With VoIP, remote administration is far more economical. This technology has re-opened opportunities for carriers to offer hosted, shared services for all forms of converged IP telecommunications, including IP-PBX and voicemail services. Because of the convergence of wired and wireless communications, such services may also include support of a variety of multi-modal handheld and desktop end user devices. This service, when offered for multiple extensions or phone numbers is sometimes also called Unified Voicemail.
Business efficiency
Voice mail's introduction enabled people to leave lengthy, secure and detailed messages in natural voice, working hand-in-hand with corporate phone systems. The adoption of voicemail in corporations improved the flow of communications and saved huge amounts of money. GE, one of the pioneer adopters of voicemail in all of its offices around the world, claimed that voicemail saved, on average, over US $1,100 per year per employee.
Voicemail has two main modes of operation: telephone answering and voice messaging. Telephone answering mode answers outside calls and takes a message from any outside caller (either because the extension was busy or rang no-answer). Voice messaging enables any subscriber (someone with a mailbox number) to send messages directly to any or many subscribers' mailboxes without first calling them. Both of these modes are described below.
Telephone answering mode
One of the advantages of a PBX is its ability to forward calls. If a person is using his phone or does not answer it, calls to his extension are forwarded automatically by the PBX to another extension, presumably someone (like a secretary) who can answer the call and take a message. With a voicemail system installed, the PBX is programmed to forward busy or unanswered extensions to a machine — the voicemail system.
Suppose an outside caller, Willma, calls someone in a company, Fred. If Fred's phone rings "no answer" or "busy", the PBX will forward the call to the voicemail system. Somehow the PBX needs to tell the voicemail system that Fred's phone is the one that the call is being forwarded to so that the voicemail system can answer with Fred's personal greeting. Without this information, the voicemail system would have no idea whose phone it was answering. Once a message is left, the voicemail system illuminates the message waiting light on Fred's phone. It does this by sending a signal to the PBX to tell it which light to light. When Fred returns to his desk and calls the voicemail system (or calls in remotely) he is presented only with the messages in his personal mailbox even though thousands of messages belonging to other people are stored on the same system. Once the messages are played, the voicemail system signals the PBX to turn off the message waiting light on Fred's phone.
Early voicemail systems (notably those made by IBM and VMX) could not answer outside calls — that is, they could not automatically answer a call originally destined to an extension on the PBX which rang busy or was not answered. As subsequent voicemail systems emerged, most notably ROLM and Octel, the systems could answer outside calls. However, most PBX's did not provide signaling to tell the voicemail system which extension it was forwarding, nor did they support telephones with message waiting lights. This signaling would come later, but until it did it created a major challenge for voicemail systems for many years.
Interoperability between systems
Voice messaging does not always have to be sent between individuals on the same voicemail system. Messages can be transferred using AMIS (Audio Messaging Interchange Specification) or VOIP (Voice Over Internet Protocol) technologies; both allow messages on one computer system to be forwarded to the target system. Like email, this method of delivering voice messages can be subject to abuse such as spam or fishing. There are Federal and State laws and regulations designed curb these abuses, such as the United States National Do Not Call Registry.
