Gadgets, widgets and interfaces

August 1, 2007

Broadcast engineering has always been a systems engineering type of job; we assemble large systems made up of dozens of pieces of equipment made by disparate manufacturers and then, through patience and diligence, expect the entire thing to work on a 24-hours-per-day, 7-days-per-week basis. I have written extensively about the large individual blocks of the typical broadcast system — consoles, transmitters, antennas and so forth — but as we all know, that isn't all that goes in to a typical broadcast system. There are unique circumstances in every radio station — some physical, some due to specifically requested functionality — that cannot always be addressed by the features of the major components of the system. What becomes necessary in many cases such as these are special devices — we'll call them gadgets in this article — that fill in those gaps and provide the last little piece of the puzzle that makes the system complete.

USB-AES Matchbox

A plethora of utility devices exist to interface audio sources and destinations

As the years have passed and the broadcast industry has matured, there has been less and less time for the typical station engineer to design and assemble the final gadgets that complete the entire system. With the typical engineer now handling IT issues, and in many cases, multiple stations, the days of in-house design and construction have, at the very least, waned. I have seen quite a few home-brewed devices such as consoles (and even the original Ampliphase transmitter), and I have designed and built many gadgets myself, but I can scarcely remember the last time I built anything.

With this trend have come more and more small broadcast equipment manufacturers making gadgets to fill in those tiny system gaps. There are many manufacturers producing hundreds of gadgets, and it would be impossible to highlight them all, but I'll share some select units I have used myself or believe would be useful to fill many of the little gadget gaps around a radio station.

A need fulfilled

Not surprisingly, most of the gadget makers are expatriate broadcast engineers themselves. Henry Engineering may be the oldest of these companies, and it makes what is probably the quintessential gadget: the Logiconverter. This device has four opto-isolated inputs and four isolated relay outputs. This allows two units to be connected electronically without the physically touching. The unit has front-panel programming allowing the user to have either latched or momentary outputs from continuous or momentary inputs. A single input can also be used to control two outputs; and conversely, two inputs can be used to control one output.

Henry makes a device that solves a more 21st century issue is the USB-AES matchbox. This little unit provides AES audio in and out of a computer by way of the USB connector. It has balanced and floating (transformer isolated) inputs and outputs and will work with any operating system that supports USB 1.1 or higher. 48, 44.1 and 32kHz sample rates are all supported with 16-bit word length.

SM HI-Plus

Some gadgets pack powerful tools into very small packages that can be tucked into a rack or mounted on a rack room wall.

Another long-time player in the gadget field is Radio Design Labs (RDL). I think its most famous product is probably the STA-1 Stick-on balanced-to-unbalanced converter. (How many consumer-grade cassette decks made it in to radio stations after this unit came out?) However, the company makes dozens of other things such as the ST-ACR1 audio-controlled relay. This unit has a DPDT relay controlled by a line-level audio sensor. The audio sensitivity on this particular one is -30dBu to 0dBu, and the time adjustment ranges from 0.5 to 5 seconds. Power is provided by an outboard 24Vdc power supply.

Not everything RDL makes falls under the Stick-on category, though. Take, for example, the FP-MX4 mic or line mixer. This device has four inputs. Each can be set for mic or line level sensitivity to feed a single bus with a line-level and a mic-level output. Power is provided by an outboard 24Vdc power supply (better known as a line lump or wall-wart). The device itself is designed to be mounted on a panel of some sort and is quite small.

Broadcast Tools has an extensive line of gadgets for the broadcast engineer. Take for example the SM-lll Plus silence monitor. This is a 4×2 audio switcher (although it can be programmed to operate as two separate 2×1 switchers) that will detect silence on a primary audio feed and then switch to the second set of inputs after a programmed delay time. The silence sensitivity is adjustable, as is the return-to-normal delay time. Alarm outputs are also provided via form-C relay contacts.

Another device made by Broadcast Tools that I have used time and time again is the SS2.1 passive switcher. I'm partial to the BNC version, and I use it as a composite switcher. This device is simply a 2×1 switcher that is controlled by the front panel or by remote control. It is completely passive — the main input is passed through to the main output even with no power applied (since it is just relays after all).

One product I have seen used with great success is the Circuitwerkes AC-12 rack-mount phone coupler bank. This is a frame that can hold up to 12 auto-couplers, each of which can be fed from one of two audio inputs (balanced and bridging). The couplers themselves have LED status indicators to show when the line is ringing and when they've connected. Each coupler has a 600Ω balanced output as well so that you can use it to drop off audio from a remote site in addition to the more familiar auto-coupler function. Another useful feature is the relay contact that each coupler has, indicating when the unit is online.

Speaking of telephone stuff, Circuitwerkes also makes a handy DTMF encoder gadget known as the Genr8. Through its optically-isolated inputs it generates DTMF tones by way of relay contacts, switches, or other logic. Using RS-232, the Genr8 can be controlled by a computer running a terminal program; programming the device is made simpler by way of a Windows-based program. Since the device includes an audio mixer, the DTMF control tones can easily be added to the payload audio.

New needs, new devices

Broadcast Devices has a broad line of devices for broadcast engineers. One particular device undoubtedly created in response to a need generated by HD Radio is the CTD-300 composite-to-AES converter. This device takes a composite input, such as that provided by a legacy radio STL receiver, and provides an AES3 output suitable for insertion into the HD Radio program chain. The sample rate is selectable to 32-, 44.1-, 48- and even 96kHz. Separation spec is 40dB from 50Hz to 15kHz, the obvious limiting factor being the quality of the composite signal coming in to the device. I should also mention that there are two AES outputs provided on the rear apron. (Take the second output, convert to audio, and you have a simple way to listen to a backup STL with no need to actually put it on-air.)

Broadcast Devices also makes the CMP-300 composite mixing and distribution system. This device has three composite inputs, each with variable gain into a single-bus, and then three outputs with individual gain controls. If you've ever tried to run multiple SCAs into an older exciter (or STL transmitter) with only one SCA input, you'll quickly see how handy this gadget is.


Some of the most useful gadgets are full interfaces, such as the Titus 3-DRX audio switcher and the DM Engineering Studio Hotline phone and door annunciator.

Titus Labs may not have the name recognition of some of the other gadget makers, and its 3DRX may not really qualify as a gadget because it's a very functional AES switcher. This 1RU device has two AES3 or 75Ω AES3-ID inputs unbalanced inputs and is primarily used to detect problems on the main input (for example loss of lock, other data errors, and perhaps most importantly, loss of decoded audio) and then switches to the secondary input manually or automatically after a user-programmed amount of time. But wait — there's more. If the 3DRX detects problems on both AES inputs, it will switch to the third input source: a set of analog inputs. It converts the analog input to digital with an internal A/D converter so that it can continue to provide an AES output. The 3DRX also has a passive failure mode. With no power applied, the main input will pass through to the output. The switching and alarm functions are available via a D-sub connector on the rear panel.

Titus also makes the Web-Rem, an IP-based remote control with a built-in Web server. User access is via the Ethernet connector, and controlled devices connect to the Web-Rem via a D-sub connector. The Web-Rem uses relays and open collector outs to provide control, and accepts analog inputs from the controlled devices, so it can provide telemetry to the remote user.

Rane makes many devices that fall in to the gadget category. My favorite device is the SM-26B mixer. This is a single-rack unit line level mixer with six mono inputs and a separate stereo input on the rear panel. Each mono input then has its own gain control and its own pan control, allowing the user to either use the mix bus in a stereo mode or a dual-mono mode. It fits the bill for just about any outboard mixing function.

Rane also makes the SAC-22 active crossover network. This device is built around a Linkwitz-Riley filter that provides phase-coherent outputs from the low-pass and high-pass filters. Primarily this device would be used to bi-amp monitor speakers, which could be very handy in a studio-build or PA function. It could also come in handy for audio processing functions.

Warnings and alerts

The first unit I noticed from DM Engineering is its Pager-Dialer. This is a small box with two input ports. The unit is programmed to seize a phone line and to dial a pre-programmed phone number in response to the input port stimulus. The numbers dialed and the DTMF strings sent may be the same or different for the ports depending upon the way the unit is programmed. This could be a very handy unit to use when a call-out function is needed, but you don't want to pay the freight for a full-blown remote control.

Another interesting device by DM Engineering is the Studio Hotline Multi. This is a multiple-line (up to 12 lines) ring detector that drives a flasher system. (One ring detector can drive up to five separate flashers.) The flashers are then located either in the studio or office space for the station; personnel are alerted to incoming calls by means of differently colored LEDs and distinctive audible indications.

In this day and age of broadcasting, most of us are consumed by the typical engineering functions such as studio and transmitter maintenance-often in addition to managing IT around the station. The days of home-brewing in-house design and construction of unique devices have for the most part disappeared. The most simple broadcast system — a studio mixer followed by an STL, followed by the transmitter — will encompass 100 percent of the system in many cases. But add remote broadcasting capability, for example, or syndication, or the generation of sports networks and the big building blocks no longer make up the whole system. Ultimately the success of the unique system will be dependent upon your knowledge, experience and creativity. Fortunately there are plenty of equipment manufacturers to fill in the gaps and provide the kind of gadgets that make up the last 1 or 2 percent of the overall system.

Irwin is the chief engineer of WKTU-FM, New York City.

Resource Guide

Selected manufacturers of gadgetsand interfaces.


A-Designs Audio

Alert System

Aphex Systems

Arrakis Systems

ATI Group


Broadcast Devices

Broadcast Tools

CBT Systems


Conex Electro Systems

Danagger Audio Works

Dixon Systems

DM Engineering

Fostex America

Furman Sound


Henry Engineering

Knights Communications

Little Labs

Lucid Technology


Opamp Labs

Prime Image

Proco Sound

Radial Engineering

Radio Systems


RCI Custom Products

RDL (Radio Design Labs)

Rolls Corporation

+44 1789 768870

Sine Systems


Sound Devices


Titus Technological Laboratories

Ward-Beck Systems


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