The humble phone-in has been a long-standing staple of TV and, even more so, radio over the years. But now technology is bringing video feeds and social media messaging from people's computers on to TV screens and the airwaves, with managing incoming calls a major part of the production.

The internet and, more specifically, video and audio over IP has been a powerful force in this new form of audience participation. It has also given broadcasters more freedom and flexibility in getting contributions from reporters and political commentators, who are able to take part in programmes from wherever they happen to be at the time: the office, out on location or at home. Widely available technologies such as Skype do not have the same picture quality as professional broadcast circuits but because viewers are used to seeing them through their own computers they seem less put off, particularly if the audio is clear.

Skype has been embraced by many broadcasters worldwide, ColorsTV in India and the UK's BSkyB among them. ColorsTV, a Hindi-language channel, used the technology for last year's run of India's Got Talent (IGT) to both get viewers involved and bring in live footage from other parts of its broadcast centre. This set-up used Riedel Communication's Skype TX in Media system running eight STX-200 interfaces connected to a MediorNet Compact network, controlled from a dedicated control room.

Sky News is getting viewer feedback to the issues of the day on its rolling 24-hour news service through four NewTek TalkShow systems. The broadcaster had been using other versions of Skype to put video calls on air but decided that it need a more reliable infrastructure better suited to professional broadcast. TalkShow allows the Skype calls to be managed in the control room in the same way as other video sources, with off-air talkback for screening, plus recording and format conversion.

The systems were bought for Sky News' studios in west London to allow viewers to get in touch from most types of device and contribute to live shows on the channel. "We found TalkShow to be a nice balance of performance, functionality and price," says Richard Pattison, deputy head of news technology for Sky News. "We liked the fact that it integrated easily with our existing control PC. It was also useful that it did not require audio inputs to be embedded on video."

Skype is based on a proprietary form of the voice over IP (VoIP) protocol that runs on a peer-to-peer basis, rather than a client-server model, which favours more integrated networking and control. Consequently manufacturers like Riedel and NewTek have to integrate a degree of management and network capability into their systems, allowing broadcasters to line up and handle several calls simultaneously.

IP-based technologies for both video and sound are becoming the norm for carrying media in general and broadcast contributions in particular. On the sound side audio over IP (AoIP) is already supplanting ISDN (integrated services digital network) and POTS (plain old telephone lines). The majority of communications manufacturers continue to support both but ISDN is slowly fading out of the picture, with many countries, notably Sweden, not allocating any new circuits based on the technology. "On the radio side we saw the writing on the wall more than ten years ago that circuit-switched data services like POTS and ISDN were on the way out," comments Chris Crump, director of sales at Comrex Corporation. "The constant need to reduce operating costs [and] eliminate things like costly satellite transmission services has really made IP technology not only viable but a necessity. The same holds true for the TV side of our business."

As a result, Crump says, the bulk of Comrex products now depend on IP networks for carrying broadcast quality audio and video. "Considering that the public internet is the most widely deployed data network on the planet it makes both logistical and economic sense to take advantage of technologies that utilise it," he observes. Comrex produces a range of IP codecs, including the ACCESS and LiveShot for audio and video respectively; call handling is covered by the STAC (studio telephone access centre) range, with IP capability allowing shows to be produced almost anywhere.

Crump comments that "there is a pretty wide range of requirements" that can be addressed by call management systems. These vary from simple auto-answer telephone couplers to management of multiple line telephone caller set-ups, which accommodate IP PBXs (Private Branch Exchanges, the internal telephone networks used by organisations and companies) and trunking integration based on SIP (Session Initiation Protocol), the communications standard for signalling and control of multimedia data, typically voice and video, in internet telephony.

"The ability to manage up to 12 incoming phone lines tends to be the upper limit requirement," Crump says of current broadcast productions. "These incoming lines need to be answered with a handset for screening purposes before being put on hold and then 'seized' by the hybrid to put the call on the air," he says. "Television stations in areas that have a high frequency of weather events depend on caller management systems for their weather trackers. The primary function of any of these systems to interface telephone audio with either an on-air audio console or, in the case of IFB (interruptible foldback), an audio source that provides mix-minus."

The phone-in is a staple of radio broadcasting, dating back to at least 1938 when the first director of BBC Television, Gerald Cock, took questions from listeners. The first regular show to use the format in UK radio is said, by Paul Donovan quoting unnamed sources in his book The Radio Companion, to have begun on BBC Radio Nottingham in 1968. That was the same year the phrase 'phone-in' came into use in the US, according to the Oxford English Dictionary. The OED states that British radio began using the term in 1971, at the start of the decade when commercial radio was established in Britain and the phone-in came into its own.

The key piece of equipment that made the plethora of radio talk shows possible over the years was the telephone hybrid, also known as a balancing unit. This converts incoming two-wire telephony signals, combining the bi-directional signals, into four-wire circuits so the different directions - send and receive - are separated. Hybrids also enabled a certain degree of processing to make low bandwidth phone calls more acceptable for broadcast. Such systems continue to be produced by companies including Sonifex but the advent of ISDN made the codec (coder-decoder) an equally important item of studio gear.

Among the companies more oriented towards radio call systems are Yellowtec and AVT Audio Video Technologies. Andy Mikutta, sales director for Yellowtec, producer of the b-line bold multi-line call system, comments that management systems have to be flexible and easy to use: "They should be able to handle two to six callers simultaneously, with G.722 support for high quality audio and all common I/O (input-output) formats. IP is becoming a standard because ISDN is dying, although POTS is still popular in Africa and India."

AVT produces hybrids and talk show systems based on POTS and ISDN as well as VoIP. Marketing and sales manager Ulrike Lauterbach highlights the ability to screen callers as a key requirement. "This means caller information is entered in a database and this information can be displayed for the producer and host/presenter," she explains. "Customers also often ask for a Black List feature to block callers. In bigger organisations more than one studio should be integrated, usually a main and backup studio is installed."

Lauterbach says 16 lines are usually enough for even large-scale broadcasters, with smaller systems going from one to eight callers. Social media is now a necessity, with Twitter and Facebook integrated into call management systems so presenters can read out comments. "Another feature is the common control of the call management system and the high-quality audio codecs which are typically located in the master control," Lauterbach adds.

The focus remains on audio in radio, although the DAB+ transmission format does have capacity for basic pictures, but Andy Mikutta concedes that images make sense on TV, with Skype and FaceTime making it possible to get those on air. Chris Crump comments that while video is "not always possible or practical", audio remains an important component of broadcast television: "One of our large radio/TV broadcast customers uses high quality audio with a still picture of a reporter when they can't get a camera crew on site. This is certainly more acceptable than no story at all."

IP and ISDN before it, along with HD Voice - wideband audio over telephone connections - have given journalists more freedom in connecting to the studio from wherever a story is happening. But, as Crump points out, new technologies such as IP and WebRTC - the free and open browser and mobile app supported by Google, Mozilla (Firefox) and Opera that enables real time communications between connected devices - are offering just as much flexibility in getting viewers and listeners on air. "We are just starting to see the very beginnings of end-user contribution. Smartphone technologies continue to exponentially improve in processing capability, lens and imaging quality and audio bandwidth at a very fast clip. Technologies like WebRTC make it possible for any person with a computer or smartphone to not only contribute to live broadcasts but also create their own content for non-linear viewing and social media platforms."

A relative newcomer to the contributions market is In:Quality, founded by Kevin Leach, who sees WebRTC as an "emerging and exciting technology" in broadcasting. Leach freelanced for both BBC radio and TV in news studio operations, where he spent a lot of time dealing with remote contribs. Through this he saw a gap in the market for connections using computers and IP. "I thought there should be more efficient ways to exploit existing and emerging technology to get people on air," he says. "So I worked with combinations to make the most of internet connectivity and computer technology that people have in their homes."

The result was ipDTL, which won the UK Radio Academy's Technical Innovation Award in 2013. The system uses the Chrome browser as an interface and controller to establish connections between contributors and the broadcast studio. The initial focus was radio but video capability has been added as TV productions began to look for more cost-effective and quicker ways to bring people into live programmes.

The majority of connections are over the public internet but Leach says the codecs used by ipDTL - the Opus open interactive codec for audio and Google VP8 (created by On2 Technologies) for video - are increasingly efficient at forward error correction. "This is a budget solution available to the lower end of the broadcast market," he explains, "but public connections are getting wider, faster and more reliable."

Right now ipDTL is a single source service with no call management capability but Leach hopes this will be added in the near future. "It's what we're moving towards," he says. "WebRTC offers the potential to do call handling management and there are developments coming from Google and Firefox. The future is more cohesive phone calls using IP."

Which probably applies to the whole area of contributions and call management.