The evolution of Wired Intercom


Simon Browne TV-Bay Magazine
Read ezine online
by Simon Browne & Ed Fitzgerald
Issue 93 - September 2014

Early Beginnings

What do you think was the fi rst DIGITAL communications system devised? Of course you could think of the evolution in standardised parallel data backplanes and digital ICs in the 1980s and the swathe of multi-rack Time Division Multiplexed switching systems that it enabled, but the answer is probably and simply smoke signals. We have to take a long journey to get back to that binary coded capability.

Our own humble beginnings in Clear-Com start way back in the mid 1960s, when the founder, Bob Cohen, was running sound at the Avalon Ballroom on Sutter St. near downtown San Francisco, frequented by the likes of Bay Area musicians like Janis Joplin, Grace Slick, Elvin Bishop, Joe McDonald aka Country Joe. With the advent of loud rock and roll it was realised that a technical solution was needed to better communicate between the follow spots, sound and back stage. Passing written notes or using the 52AW Carbon based telephone headsets or shouting across the loud and busy stage did not make for a smooth production. Rock and Roll was loud; levels near stage (and on stage!) could be in excess of 115db and simply throwing “louder intercom” to the ear was not the answer.

Bob Cohen came to know a young man, Charlie Butten, who was working with local bands and fi xing the guitar amps for Lindsey Buckingham (Fleetwood Mac) that kept blowing up. Charlie Butten Sound had become the ‘go to’ fi x it place for the touring US and British bands and Bob looked to Charlie to help with the better intercom need.

Between Bob’s connections and Charlie’s technical knowhow, rudimentary, clunky but effective intercom systems were provided to the touring bands for real life ‘on the road again’ tests. As the bands went from town to town, Bob started getting calls from venues around the US, “Where can we get that Intercom that The Steve Miller Band used last night?” The name “Clear-Com” (clear communications) found its genesis at this time in 1968. This is how multichannel partyline intercom started in the US.

Broadcast Intercom

US television and theatre production caught wind of the Partyline technology having seen it used on follow-spots at concerts. In 1977 for example, one of the very fi rst calls for a beltpack TV application came from WNEM-TV in Saginaw, MI. TV and Theatre drove the technology towards ever greater solutions, with connections to the broadcast 4-wire matrix becoming commonplace by the mid 1980s.

In the 1970s, European TV production was stepping up to the complexities of higher resolution UHF pictures and colourisation, and now had upward of 15-20 people all working together on one recorded or live TV show. Housemade 4-wire (a pair in each direction) CMOS and relay switched systems were not only large, cumbersome and highly customised; they could not be altered as productions changed and each new use required a complete project to accomplish. Philip Drake Electronics, beginning in 1976 in the UK, saw a need to streamline this custom approach and provided a tool set of Euro-rack, reusable and modular cards with input, crosspoint router, output and GPI cards for the BBC. Other European manufacturers also provided similar modular systems that could be designed and manufactured more quickly drove the industry toward standard matrix based intercom solutions.

System modularity certainly helped in providing repeatable solutions across Europe but once wired in the rack frame, changes were hard to make and a complete re-wire and full input to output crosspoint test would have to be done. The down time made this option a last resort and there was a need to fi nd a way to make changes much easier.

In the 1980s microprocessors and on-board memory made it possible to hold the ‘routing tables sent from a user confi gurable PC database in CPU card memory. Now all the user panels could have confi gurable keys to talk to selectable destinations that could be changed in almost real time. Thus a small news studio set-up could be changed for an evening recording of a game show with live audience all within the same studio and control room. The one full and a half intercom equipment racks went from 40-60RU down to one equipment rack of about 30RU for 96 ports, including interfacing cards to lines and cameras and for the DC power supplies.

In the 1980s we saw standardised products from US and European manufactures using modular, PC confi gurable systems for intercom solutions. In 1989 for example Clear-Com in the US introduced the compact Matrix Plus system, Drake in the UK brought out the 6000 and Trilogy Broadcast in the UK with their Commander system. McCurdy, later bought by Telex in 1990, added their early matrix solutions to the growing options for the global TV broadcast industry.

These systems had panel connections that carried audio, power and serial data with 12 to 25 core screened multicore cables between the central equipment matrix frames and each of the outstation panels. The TX/RX serial data removed the requirement to have an ‘activation wire’ per panel switch, which could be as many as 48 switches. However it wasn’t until full digitisation of intercom in the early 1990s that the equipment became almost portable.

Getting Back to Digital

In 1992 the Barcelona Olympics used one of the fi rst fully digital 192 x192 intercom matrix in just 9RU (~15 inches). In digital intercom systems, panel and 4-wire audio is digitised using PCM audio and sent through a single, and sometimes redundant, digital crosspoint card where once there had been many such cards, one for each group of ports. The panel connections now often used co-axial video type cable to carry bi-directional AES audio with local power at the user panel. Every manufacturer’s design was more compact and more reliable with redundant switching and single crimped co-axial cables to the panels.

By the new millennium almost all broadcast and large theatre matrix intercom systems were somewhat digital, with manufacturers in both the US and Europe providing systems based on proprietary or as with Riedel in Germany, AES3 router solutions. These matrix systems still had to connect to partyline wired systems and audio connected analogue wireless VHF and UHF systems, but there was a growing need to connect to Telco IT lines such as ISDN, T1 and even Audio/data modems. These allowed users to be remote not just by being in the next building but in the next country! Soon larger public broadcasters in Europe and the US were tying together all their production centres with one multi-frame networked intercom system over ISDN. These were highly nuanced and complex systems and the technology designed for data transport had to be teased to give reliable performance with voice.

IP Technology

1994 started to see IP Telecommunication companies offering ubiquitous network solutions over Ethernet IP for telephony and data, and by 1997 most intercom manufactures had IP interfaces so that users in temporary news set-ups in hotel rooms could connect back to the production intercom systems in London or New York, or both over low-cost VPN lines. IP has enabled remote connections and ease of set-up within intercom to become the norm. PC, Mac or Smartphone applications can now provide ad-hoc client intercom ‘panels’ that can be downloaded and in use within minutes, complementing the more traditional digital intercom systems. Today, where once IP technology was on the periphery it is now found in the centre of modern communication systems. The next generation of intercom systems may exist wholly inside the IP domain offering easy to use, ad-hoc fl exibility with fully featured touchscreen technologies working alongside customers’ cellular devices in one big distributed network; and that’s not just blowing smoke.

www.clearcom.com


Tags: iss093 | Clear-Com | Wired Intercom | Ed Fitzgerald | Simon Browne
Contributing Author Simon Browne

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