A conference call is a telephone call in which the calling party wishes to have more than one called party listen in to the audio portion of the call. The conference calls may be designed to allow the called party to participate during the call, or the call may be set up so that the called party merely listens into the call and cannot speak. It is often referred to as an ATC (Audio Tele-Conference).
Conference calls can be designed so that the calling party calls the other participants and adds them to the call. In most cases, the participants are able call into the conference call themselves, by dialing into a special telephone number that connects to a "conference bridge" (a specialized type of equipment that links telephone lines).
Usually, most companies use a specialized service provider who maintains the conference bridge, or who provides the phone numbers and PIN codes that participants dial to access the meeting or conference call.
Three-way calling is available (usually at an extra charge) for most customers on their home or office phone line. To three way call, the first person one wishes to talk to is dialed. Then the Hook flash button is pressed and the other person's phone number is dialed. While it is ringing, flash is pressed again. This will put the three people together. This option allows callers to add a second outgoing call to an already connected call.
Conference calls are used by nearly all United States public corporations to report their quarterly results. These calls usually allow for questions from stock analysts and are called earnings calls. A standard conference call begins with a disclaimer stating that anything said in the duration of the call may be a forward looking statement, and that results may vary significantly. The CEO, CFO, or Investor Relations officer then will read the company's quarterly report. Lastly, the call is opened for questions from analysts.
Conference calls are increasingly used in conjunction with web conferences, where presentations or documents are shared via the internet.
Conference calls are also beginning to cross over into the world of podcasting and social networking, which in turn fosters new kinds of interaction patterns. Live streaming or broadcasting of conference calls allows a larger audience access to the call without dialing in to a bridge. In addition, organizers of conference calls can publish a dial-in number alongside the audio stream, creating potential for audience members to dial in if and when they wish to interact.
In the UK, there are conference services offered on a pay as you go basis where the cost of the phone calls (using 0844, 0870 or 0871 numbers) from each of the participants covers the cost of the conference service. With this service type there is no monthly charge and usually no contracts to sign.
Large telecommunications providers such as AT&T, Embarq (formerly Sprint), Verizon and other large to medium conferencing service providers maintain a dominant position in the conferencing niche; servicing many of the World's biggest brands. However, the Internet and improved global VoIP networks have helped to significantly reduce the barrier of entry into this niche.
Free conferencing is different from traditional conference calling where the organizer of the conference call pays either a flat rate fee or per minute charge or a mixture of both. It has no organizer fees and allows for multiple people to meet at the price of their long distance connections.
The 3rd Generation Partnership Project (3GPP) defined a technical specification (TS 24.147) for conferencing within the IP Multimedia Core Network subsystem (IMS) based on the Session Initiation Protocol (SIP), SIP Events, the Session Description Protocol (SDP) and the Binary Floor Control Protocol (BFCP).