Taking the show on the road
Feb 1, 2006 12:00 PM, By Doug Irwin
Successfully creating a remote broadcast is much easier now than it ever was before. As recently as 15 years ago there were only two options for a remote broadcast: buying an audio line (or lines) from the telephone company or using a radio link (probably a 450MHz system). Switched 56 and ISDN were in their infancies, and there was no equipment available to make use of them. For all intents and purposes there was no Internet; no cable or DSL. Go back even farther (a little over 20 years) and you'll recall that to talk with the studio from the remote site we used a telephone (a regular dial-tone) and a long piece of wire to hook it up. A stereo music remote required the station to order two lines, which also required the station engineer to visit the remote site ahead of time to test both lines for continuity, frequency response and phase response. The telephone company used to call this �stereo conditioning.�
I'll admit that I don't miss that part at all.
As technology has progressed, the telephone company has found more and more ways to use the same old copper wires buried in the ground so many years ago. In Seattle we still use 8kHz audio lines for the home games of the University of Washington Huskies because it sounds better and it's easy to test remotely. We still use dial-tone for POTS codecs, too. ISDN is ubiquitous, although there is more and more talk of it disappearing. Part of the reason for that, I suppose, is that the telephone company wants to use the same copper wires to carry more and more data, such as DSL. Fortunately, codecs that use DSL and Wi-fi are now available for use.
And don't forget about the old-fashioned radio systems. New versions of the same old analog radio systems are still made and still serve a purpose. Cellular telephone technology has evolved as well and has greater potential for use in carrying out remote broadcasts.
The current state
Currently, Tieline has introduced the I-mix G3, which is a complete remote broadcast package with a built-in mixer. The I-mix has an expansion slot that can accommodate another POTS codec, an ISDN codec or a GSM module. The POTS codec plug-in can be used with the built-in unit to bond two analog phone lines together, providing mono, stereo or dual-mono audio feeds with a 15kHz frequency response. The ISDN codec uses G.711, G.722, MPEG Layer 2 or Tieline's own music algorithm. The GSM module provides 7.5kHz of audio bandwidth on the standard GSM network or 15kHz over a high-speed HSCSD GSM network. (The GSM module communicates with a standard POTS codec on the far end.) Tieline's IP software module gives the I-mix the capability to connect to wired or wireless LANs. (To use the I-mix with a Wi-fi network the user simply provides a mini Wi-fi bridge, and then connects it to the I-mix via the RJ45 Ethernet connector.) Audio performance over an IP connection can go as high as 20kHz, stereo, non-compressed, although this requires a data rate of 2.5Mb/s.
Comrex has many years of experience in building equipment for remotes over plain old telephone circuits, and, not surprisingly, its current line includes all the features and functionality that you would expect. The Matrix is the company's flagship product. The studio end would typically be the rack-mount unit; the Matrix Portable is the unit typically used in the field. It features a remote mixer with one mic-level input, one mic or line level input, a headphone output and a line-level out. Typically the Matrix uses an on-board POTS codec that can provide up to 15kHz of duplex audio response depending on the quality of the POTS connection. However, the user can also add modules to the Matrix such as the Portable ISDN module, the Matrix GSM module or the Matrix Telcell module.
Comrex is also finalizing a new product called Access, which takes advantage of the increasingly diverse set of connection possibilities: POTS, DSL, cable DSL, 802.11x (Wi-fi), 3G data networks, high-speed cellular data networks and the public Internet. It uses the Comrex-developed BRIC (Broadcast Reliable Internet Codec) and will perform at several user-selectable quality levels. HE-AAC and AAC low-delay are also available for use over robust networks.
Musicam is a long-term player in the field of POTS and ISDN codecs. One of several such codecs is the Roadrunner, which is a compact, portable ISDN codec with a built-in mixer. The unit has three-inputs; two at mic level, and one that switches between mic and line level. The unit can deliver 20Hz to 20kHz audio bandwidth with a SNR of 84dB when using both B channels of the ISDN circuit; it can achieve 15kHz audio bandwidth with only one B channel. The Roadrunner offers the choice of G.722, Musicam enhanced Layer 2 and MPEG Layer 3 algorithms, with connection rates from 56 to 128kb/s.
Musicam also manufactures its own codec that will work via IP: the Netstar. This unit can send and receive high-fidelity audio, contact closures and ancillary data via ISDN, dedicated data lines or IP. It contains the standard algorithms such as G.711, G.722, MPEG Layer 2 and MPEG Layer 3 as well as MPEG AAC and MPEG Layer 4 AAC-low delay. Like the other IP codecs, this unit can deliver uncompressed, 20kHz audio with near-zero delay if the IP connection supports it.
The APT Tokyo is yet another full-featured, multiple algorithm codec. In addition to MPEG Layers 2 and 3, G.711, G.722 and MPEG AAC, it also includes APT proprietary codecs such as Standard Apt-x and Enhanced 16, 20 and 24-bit Apt-x. This device features a built-in inverse multiplexer that allows it to use as many as four ISDN circuits, and hence up to 512kb/s data rate. It can also be used over a LAN or WAN, by way of its Ethernet connector or via USB.
AEQ makes several audio codecs, including the Eagle and the Swing. The Swing is a portable codec with a U-interface and S-interface and the standard ability to use one or both B channels of an ISDN circuit. It includes a built-in mixer and headphone amp, and also a digital telephone hybrid. The Eagle is a rack-mount unit that features a dual ISDN interface (U and S); standard algorithms for use with a single B-channel, such as G.711, G.722 and MPEG; the standard capability of bonding both B channels for the full 128kb/s data rate; and the capability to use one B channel for a plain old telephone. It comes with two back-lit displays: one for dialing and one for menu configurations.
Audio TX sells a software package called Communicator that allows the user to turn a PC or a laptop (with an audio card and an ISDN card) into an ISDN codec. The software (compatible with Win 98, NT, Me or XP) includes algorithms for MPEG Layer 2, Layer 3, G.722 and G.711, and can connect with other manufacturers' codecs. The Communicator can also be used over IP through physical connections such as a LAN, Wi-fi and DSL.
The Scoop Reporter E-Z from ATA is another portable remote package, and it has an ISDN and POTS codec built-in. The unit includes a three-input mixer (two mic and one selectable mic/line) and two headphone outputs. MPEG, G.711 and G.722 algorithms are included.
The Orban Opticodec 7000 is a portable device that includes an ISDN codec with the standard algorithms-G.711, G.722, and MPEG Layers 2 and 3. The Opticodec's unique feature is that it includes a built-in digital audio recorder and editing system.
Telos Systems' latest ISDN codec is the Zephyr Xstream, which now includes the MPEG4 AAC low-delay algorithm. The Zephyr Xport is its POTS codec that can be made into an ISDN codec as well with the inclusion of the field-installable ISDN option. The Xport uses AAC Plus audio coding for POTS connections; MPEG AAC low delay for ISDN connections made with an Xstream on the far end; and its G.722 option allows it to communicate with other G.722 codecs as well. The unit offers a built-in mixer with mic and line-level inputs, and independent headphone outputs that can listen to received audio and monitor mixes.
Off the wire
Perhaps you are doing a remote 500 yards away from the nearest telephone company demark and there are no POTS lines, ISDN or DSL. Perhaps there are no coffee shops nearby and thus no Wi-fi. Or, maybe you just want to skip wire altogether and use a radio shot for your remote. Well, you're in luck because RPU equipment is still made.
TFT offers the 8888 RPU transmitter and the 8889 RPU receiver. The system includes frequency-agility, selectable deviation on the transmitter (with 20W RF output) and selectable bandwidth on the receiver. The receiver can be controlled remotely with DTMF tones, so that its operating channel and IF bandwidth can be changed. The transmitter includes a built-in mixer with three mic or line-level inputs; a send/return loop for connection to an external audio processor; a built-in peak limiter, and a headphone output for monitoring of the locally mixed audio.
Marti has recently introduced a new RPU transmitter--the SRPT-30. This unit comes with two (factory selectable) frequencies; four front-panel mic level inputs (line level input available on DB connector on the back of the unit) going into its built-in mixer; and up to 30W out. The SR-30 is the current model RPU receiver.
If you get stuck in a situation that there are no phone lines and no way to get an RPU shot out of the remote site, then you could be saved by the Marti Digital Cellcast. It uses a radio link through a digital cellular system for its connection back to the studio; a GSM version is also available. The unit includes a four-channel mixer, with line in and line out connections.
As broadcasters compete with other content providers it is becoming clear that the remote broadcasting is unique to radio. It's a great way to have interactivity with the audience and it often makes clients happy as well. Having a reliable and functionally simple remote system is quite often the key to success of a radio station's engineering department.
Irwin is director of engineering at Clear Channel, Seattle.
Manufacturers and suppliers of codecs, codec accessories and RPU equipment
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