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Mad about audio

I'm a student electronics engineer in Belgium. I have to make anessay about MADI. I can't find any information about it. Can you give me more information about what it is and how it works?
Kim Verbeke

From Broadcast Engineering's sister publication, BE Radio:

MADI is an abbreviation for Multichannel Audio Digital Interface. It is a standard described by the Audio Engineering Society (AES) standards committee as AES-10 and AES-10id. With it, 56 channels of audio in the form of 28 AES-3 (AES/EBU) format signals can be sent across a single cable. (A single AES-3 channel has two channels by definition.) Its purpose is to provide a more simple means of distributing many channels of audio without the need of multiple cables or paths.

A MADI signal is transmitted via coaxial (AES-10) or fiber optic (AES-10id) cable. These signals are multiplexed — not compressed — so it is a lossless transport mechanism.

MADI is used within facilities to send many audio channels from one point to another. Many routing switcher manufacturers use MADI to connect multiple inputs and outputs to their distribution matrix. Large console manufactures also use MADI to simplify their input configurations. Some facilities use MADI simply as a point-to-point distribution method to reduce the cable requirements.

You can purchase a copy of the formal standard by contacting the company that publishes all the Audio Engineering Society standards, Global Engineering Documents, at 1-303-397-7956, 1-800-854-7179, or online at
Chriss Scherer
Editor, BE Radio magazine

Need Townsend parts?

Recently a reader asked for help in locating parts for Townsend transmitters. Here's a source: Dave Compton 304-622-9622 or 304-622-9839.

Turn on the lights

I am trying to identify a light control unit associated with one of our towers. Attached is a picture of it. Do you recognize this lighting control? Can you help me locate someone who could supply parts?
Jim Barnes

The question was passed to our transmission guru, Don Markley. It took him about 20 minutes to locate the answer. The tower lighting unit is a ROHN FA2SS1, built around 1982. Parts are still available from:

ROHN IndustriesInc.
P.O. Box 2000
Peoria, IL 61656
800-225-7646; 309-697-4400
Fax: 309-697-5612

Recent Freezeframe winners

December: “Identify the FCC chairman called both “visionary” and a “one-man wrecking crew.” The correct answer was Mark Folwer. Shame on those of you who have (or used to have) First Class licenses. Mr. Folwer was responsible in getting that license eliminated.

Correct answers supplied by:
Tom Anderson
Spokane, WA
Mike Norton
Wisconsin Public Television

January: “What (now renamed) company introduced a 7lb ENG camera at the 1976 NAB convention calling it the “Women's lib camera?” The camera was introduced by Thomson-CSF Labs and officially called the Microcam. Fully loaded it weighed 12.5lbs. The whimsical name didn't stick for obvious reasons.

Correct answers supplied by:
Dave Kosh
Waterman Broadcasting
Tom Anderson
Spokane, WA

Don't miss this month's Freezeframe question on page 8. Answering the question correctly will win you one of the newly designed Broadcast Engineering T-shirts and fame by being published in this magazine.