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Remote Broadcast Access

Newsletter Issue 6

Inside this issue:

Comrex Comments

by Lynn Distler
President, Comrex Corporation

This Access issue centers around our new Matrix codec. One of the first customers in line for the Matrix was the White House Communications Agency. For the past 10 years, the WHCA has been covering presidential travels with dozens of Comrex two-line frequency extenders. It was time to upgrade.

The Matrix flexibility made it a perfect fit. No matter what circuits are found in any part of the world - POTS, ISDN, Wireless, Satellite - the Matrix provides a way to send the best possible quality audio back home. We're very proud to have the new Matrix in place at WHCA and hope they have as long and as useful a life as the two-lines.

One important note on the Matrix. The fast pace of technological advances has accelerated the rate of our new product development to an almost unconscionable level. On one hand, it is our mission to take advantage of new communications circuits and audio processing approaches in the design of Comrex products. On the other hand, we, and our customers, expect longevity from these products. The Matrix's design provides a "future proof" insurance policy. For example, digital wireless offerings will expand dramatically in the next few years. When this occurs, a new accessory module and/or a flash upgrade will allow present Matrix users to take advantage of these new wireless offerings

All-in-One Matrix Goes to Mexico

by Allen J. Singer, Assistant Engineer, WRRM(FM), WMOJ(FM)

At WRRM(FM) Warm 98 and WMOJ (FM) Mojo in Cincinnati, we have both the HotLine and the new Matrix. The Matrix uses the same codec as the HotLine and Vector, but has added flexibility for future expansion and changes in technology. Jim and Randi in the morning


The Matrix is a strong addition to our remote broadcast equipment arsenal. Warm 98 does a fair amount of live remotes, but Mojo - a jammin' oldies station - requires live broadcasts and constant live appearances.

Even if a remote consists of three breaks an hour, we need equipment flexibility. That is why we use both the HotLine and Matrix, sometimes simultaneously.

Warm 98 and Mojo have been using the Matrix for almost three months in shopping malls, nightclubs and bars. One of the first times the Matrix was used was when we did "Mojo Mexico." The morning show broadcast live from Cancun, Mexico in October 2000. We had arranged for a phone line to be installed, and the line worked the night before the broadcast. The morning of the broadcast, the line had been pulled. My boss, Kevin, the chief engineer, was on site in Mexico. I was at the station in Cincinnati running the show there. Kevin ended up plugging the Matrix into a hotel phone jack (which Comrex did not recommend). I had to call the hotel front desk using a phone plugged into the studio Matrix, and ask the clerk connect me to that extension. I then switched the Matrix to connect when the far-end Matrix answered. After we figured out how to do that, the remote went fine.

Our staff likes the flexibility and portability of the Matrix. We don't need an external mixer when we use the Matrix, and the promotions department can easily break the equipment down after a broadcast without engineering help. Since the Matrix contains its own mixer, the extra equipment needs are minimal. Normally all we need is the Matrix, a couple of mics and headphones. And with this small amount of equipment and a phone line, we can do a remote practically anywhere.

For more Matrix information, return the enclosed reply card or email us at info@comrex.com.

Matrix and Red Sox - Both Winners

Spanish Beisbol NetworkIt was a great start to the Red Sox Season! As a long time citizen of Red Sox land and one who has totally given up on any chance of a World Series win, it was with a little trepidation that I accepted the assignment to take photos of the Matrix in action.

Bill Kulik had acquired the rights for the Spanish Beisbol Network to broadcast the Boston Red Sox. This is their first year of operation (WRCA 1330 AM, known locally as Caliente 1330, is their flagship station) and they wanted to do it right but with as much economy as possible. Bill and Spanish Beisbol chose to go with the Comrex Matrix Audio Codec, incorporating the ISDN modules. As Miles Smith, the contract engineer for the job, explained "This allows them to use ISDN where possible and POTS where ISDN is not available, yet learn only one piece of equipment. How easy can it get?" Everything was set and they were going to do their first broadcast with the Matrix on opening day at Fenway Park.

Bill arranged for a pass and I was able to avoid the long lines, heading right up to the the 5th floor press area. There was the Matrix - sitting alongside a mixer and on top of the DAT player. This was it - all the equipment needed! The three announcer microphones and crowd noise feed from the park were sent into the mixer. This was fed to the Matrix. Back at the studio was a Matrix Rack waiting to receive the play-by-play and put it on the air.

When I arrived, Miles was doing a training session for Bill and Steve 'El Gato' Katsos. The phone numbers were programmed already so all they had to do was hit "Q-Dial" and watch the level light to make sure they were not overdriving. It was actually pretty boring as the unit dialed, made its connection and never had to be touched again. As Bill said "Not much excitement and very successful. Just what we want!"

I took my pictures, the Red Sox won the game and everyone went home happy - especially the guys from Spanish Beisbol Network!

Store & Forward, Wireless GSM and Other Matrix Features

The Matrix is by far the most complex audio device we've ever delivered, and it has so many features that we'd like to outline some of them. Of course, it's a great POTS codec, capable of 15KHz two-way audio on a normal phone line, but it's also much more:

  1. Store and Forward - The Matrix can record audio (using the same technique it uses to encode audio for phone lines) and play it back. The internal flash memory of the Matrix can hold 10 minutes of recorded audio. Once recorded, this audio can be sent like a computer file to another Matrix in non-real-time. This can be really useful for applications that don't require two-way interaction, but do require high fidelity audio on poor circuits. Store and Forward mode can also be used on most wireless phones.
  2. Wireless operation - When used in conjunction with certain GSM wireless phones, the Matrix can send real-time 5KHz audio over the digital telephone link. While the audio quality doesn't rival what the Matrix can do on wired phone lines, it's an important first step toward what the Matrix will be able to do when high-speed wireless services are available. (Note to European Matrix users: If your GSM provider supports HSCSD*, the Matrix can already provide up to 10KHz audio on GSM!) Also, with some new Nokia phones, no additional modules are required to connect to your GSM phone.the phone's data cable connects directly to the "Multipurpose port" on the main Matrix housing.
  3. Matrix Rack POTS/ISDN auto-switching - The Matrix rack can auto-answer either an incoming POTS or ISDN call and adapt automatically to encode and decode audio on that line. This means if your ISDN fails, you don't need to change anything in the studio to change to POTS backup.
  4. ISDN international compliance - The Matrix ISDN module can be user configured for either "U" (for North America) or "S/T" interface (for international operation) and has switch protocols for virtually any ISDN line worldwide.
  5. Manual rate drop and retrain - In POTS mode, the connect rate can be dropped one "notch" for enhanced reliability with a single button push. Push the button twice, and the Matrix will do a complete handshake with the phone line without dropping it. You can also configure whether the Matrix will automatically initiate a new modem handshake when the line gets bad.*
  6. More - The Matrix will automatically dial either a POTS line or ISDN line on a contact closure ... makes a great STL backup. Configuration information for 10 ISDN lines can be stored in the Matrix. Ancillary data is available in both POTS and ISDN modes. Turbo G.722 in ISDN mode combines high audio bandwidth with minuscule delay.

For a complete list of features, send in the attached reply card, check out www.comrex.com or give us a call.

* See "Tech Tips" below for further details.

TechTips:

HSCSD

Matrix wireless operation is constrained because standard GSM service provides only 9600 baud for data transfer, which is a very challenging data rate for high quality audio. Since it's also a very low speed for web surfing, a new GSM data standard has been introduced called HSCSD (High Speed Circuit Switched Data) that combines 2 GSM voice channels to provide higher speed wireless data. HSCSD is now deployed in many European countries, delivers up to 28.8 kb/s wirelessly. You will need to buy specific phones to work on this service. (The Nokia 6210 is the one we're using for our tests.) Our initial testing shows the ability to transfer 7 to 10KHz audio over this service. Check out the Comrex website at www.comrex.com/wireless.html for updates about this and other wireless advances.

Disabling Auto-Retrain

When a Matrix user is plagued with a bad phone line, the result can be repeated retraining (audio drops for 7 seconds while the modems shake hands). In some situations, this can be avoided. For example, if a station is broadcasting a baseball game, they may be using the Matrix in only one direction, from the venue to the station, and not utilizing the return channel to the venue. But the Matrix will initiate a retrain even if only the modem data going to the venue is corrupted. In this case, the users may benefit from disabling the ability of the remote Matrix to automatically renegotiate. This may result in a more reliable link to the station and a less reliable one to the venue (which isn't being used anyway). The Matrix Manual describes how to set your Matrix this way, but read the cautions about operating in this mode.

Ask the Codec Answer Guy

Codec Answer Guy

Q. I am buying a Comrex Matrix. Will it work OK with my HotLines and Vectors?

A. Ahh. a steady customer! The Codec Answer Guy well knows the connection between folks like you and his paychecks! The Matrix will automatically realize that it is talking with a HotLine or Vector and will switch to the appropriate mode. Unless your Vector or HotLine is very new, or has been upgraded recently, you should contact us about an upgrade that will insure maximum happiness with the newer modem in the Matrix. Also, you may want to turn off the Error Correction feature on the HotLine, particularly when used with the Vector.

Q. When I reprogram the SPIDs on my Nexus, I sometimes get a strange error message, like 'SS62'.

A. Since ISDN was invented by aliens from the planet BZ8S, we are stuck with a few quirks from their culture. First, they speak only in acronyms. "SPID" is a sacred word there, and they thought they were giving us something of great value. Second, out of reverence to that sacred word, they never presume to reprogram their equipment unless they first pull out the ISDN line. You must imitate their example, and not change your SPIDs without disconnecting the line, lest the curse of "SS62" fall upon you.

The Answer Guy is happy to respond to your questions. Send an email to answerguy@comrex.com or fax questions to 978-635-0401.

GSM Tips

GSM - What it is and where to get it.

Worldwide, GSM is the most common standard for digital wireless phones. However, in the US, there are three digital wireless standards that are widely used. At this time, GSM is the only form of digital PCS that has a stable enough data spec to be suitable for audio codec use. Most major cities in the US and Canada have a GSM carrier. We have listed some of the largest carriers in the US and Canada as well of some websites that can help you determine service and coverage in your specific area.

T-Mobile Wireless - widespread in US- www.T-Mobile.com/products/coverage/local.asp

Powertel - covers much of the South - www.powertel.com/htm/lea/lea_cov.asp

PacBell Wireless and Bell South have been assimilated under the Cingular umbrella (along with many other carriers). So some Cingular customers have GSM available to them. It is best to check one of the GSM websites:

To search for a carrier by state and a good overall GSM website:
www.gsm-pcs.org/coverage_cities.html.

For coverage maps by cellular provider:
www.gsmworld.com/gsminfo/cou_us.htm.

For Canada and most anywhere else in the world: www.microcell.com.
At the top of the page (yellow bar), click on 'sections', then 'coverage'.

Since this is a rapidly moving field, we suggest you make frequent checks to our website: www.comrex.com/TechNotes/tn219.htm for updates on GSM providers and other wireless advances.