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Newsletter Issue 7

Inside this issue:

Comrex Comments

by Lynn Distler
President, Comrex Corporation

Our lead story in this issue is about the BBC using our Matrix codec on the high speed GSM cellular service available throughout the UK. While at the SBES convention last November, I was impressed with the performance of the Matrix on this service and talked with BBC engineers who were just starting trials with the Matrix on GSM. This is now part of their standard operations.

The bad news is that this high speed service is not yet available in the United States, and therefore, the utility of the Matrix on cellular services is limited here. The good news is that our close involvement in international markets has allowed us to do the necessary development work so our products will be ready when the US services catch up to countries like England and Japan.

As you can see from this issue, Comrex is going full tilt. Our new building will double our present space. Everyone at Comrex has been active in the design process, and we are looking forward to an attractive, productive new home. In addition to this major construction project, we just started shipping the BlueBox. This replaces the original HotLine POTS codec, introduced in 1997, and provides twice the audio quality plus operation on wireless services - at the same low HotLine price.

We have plenty on our plate for the remainder of 2002. Thanks to our great customers for keeping us busy with challenging and interesting projects.

BBC - Mobile Zone goes wireless with the Matrix

by Ian Prowse - Vortex Communications (UK Comrex broadcast dealer)

Now that the GSM cellular service known as HSCSD (High Speed Circuit Switched Data) is available throughout the UK, the BBC is using the Matrix on almost a daily basis to deliver wireless full duplex live feeds with up to 10 kHz audio bandwidth.

Blackburn City bus in which the Mobile Zone is based

Twas on a cold windy day that I set off up the M6 to Blackburn to meet Samantha Fenwick and Carol Turner, reporters with the BBC Radio Lancashire Mobile Zone. As part of the BBC’s “return to its roots” Radio Lancashire in Blackburn has an open door policy where the general public can visit the Radio Zone, the Learning Zone, the Web Zone and the Interactive Zone, whilst out on the road is a Blackburn City bus in which the Mobile Zone is based.

The bus is equipped with a coffee machine, six computers for web browsing and a small radio studio equipped with mixer, MiniDisk recorder, a couple of wireless microphones and headphones plus a Matrix to send the programme audio back via POTS/PSTN and GSM.
On broadcast days (5 each week at present) the Mobile Zone parks in a different place such as a pub car park, outside a parade of shops, inside a prison, next to a railway station, from where it opens up for business. It either plugs into a nearby phone line or if this is not available, the Matrix offers wireless communication via GSM. Members of the public can pop along and try their hand at web browsing with friendly BBC helpers to lend a hand. Meanwhile a half-hour programme plus a couple of shorter inserts fall into place, giving a picture of local life as it happens.

People On The Bus

On the day I visited the Mobile Zone, the BBC was going wireless with the Matrix. The bus was parked outside a flower shop that had just completed the flowers for a biggish funeral and from where Carol Turner - that day’s reporter - started her story. Equipped with a wireless mic, she popped into the hairdressers next door where one of the technical coordinators was being pampered in the tanning salon and, as the programme continued, Carol and Samantha found a tattoist, a vet, a couple of soldiers from the local army barracks and a lady who had a wealth of reminiscences of her life in Watling Street Road (built by the Romans around 45BC). REAL RADIO with REAL PEOPLE!

The BBC Lancashire Mobile Zone is the first of a number of buses about to go on the road in places from Humberside to Cornwall, this time to be equipped with Matrix codecs working on POTS/PSTN, ISDN and GSM.

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

Park City NPR Affiliate Depends on Comrex for 2002 Winter Games

by Chris Eisenberg - KPCW, Park City, UT

PARK CITY, UT ­ As the only local radio station based in Park City, UT, we at KPCW ­ 91.9 FM knew our station would be a crucial source of information for locals and visitors during the 2002 Winter Olympic Games.Matrix at 2002 Winter Olympic Games

With our small mountain ski town playing host to three Olympic venues and a public celebration that required the three-week closure of the town’s Main Street, we anticipated a community-wide interest in everything from traffic reports to weather forecasts to daily briefings by city, county and transportation officials.We made the decision early on to go all news from February 9 ­ 24. The challenge was how to get live, high-quality audio feeds from the various briefings open to all members of the media without having to install ISDN lines. While a wireless link was an option in some cases, our frequency was shared with other users. This meant we might not be able to use the link every time we needed it. And then there was the need for a back up in case the wireless system failed.

The solution turned out to be a combination of Vector and Matrix audio codecs from Comrex Corporation, based in Massachusetts. Both the Vector and Matrix allow the user to send and receive high-quality audio over a standard telephone line. Additional connections allow users to add mic or line level audio and to tape the feed as it’s being sent down the phone line.
Based on my experience using other kinds of audio codecs, I was anticipating having to spend a lot of time fiddling with settings to get these units working. But it wasn’t like that. We literally plugged the Comrex units in, fed them audio, dialed a phone number, and they worked.

During the 17 days between February 9 and 24, KPCW used both the Comrex Vector and Matrix to broadcast numerous press conferences and interviews, including an address by former New York City Mayor Rudolph Giuliani. The units were also used numerous times to feed audio cuts back to the station.

Over the entire stretch, we aired close to 12 hours of audio that came over the Comrex units. And it sounded great.

We’re grateful to Comrex for their generous support.

BlueBox - Full fidelity on POTS at a fraction of the cost

Blue Box

We are proud to introduce Comrex’s newest addition to the POTS codec line! The BlueBox delivers the same audio quality of the Matrix and Vector codecs at a fraction of the price. This low cost codec doesn’t skimp on quality or features, offering many of the bonuses of the Matrix. In addition to delivering 15 kHz on POTS and offering compatibility with the popular HotLine, Vector and Matrix POTS codecs, the BlueBox provides a data port for interface to GSM wireless phones. Also, a mini-jack provides easy connection to the hands-free port on mobile phones to place calls to telephone hybrids (no codec is required on the receiving end of the call). While this phone patch does not add any audio enhancement to the wireless call, it makes a useful backup tool. Professional quality microphones will often make a substantial difference in audio quality.

The BlueBox includes one mic/line switchable input, one headphone output, one line level output, and a -10 dBu tape input allowing connection to a minidisc or DAT player. Whether for a breaking news story, a sports event, a hot celebrity interview or a last-minute remote, the BlueBox is the right choice.

Ask the Codec Answer Guy

Codec Answer Guy

Q. My power connector is flaky. Should I replace it?

A. If the power jack on your HotLine or Nexus has the letters “SWC” visible from the back of the unit, we would like to see it replaced. Otherwise (or if you own a Vector), a little cleaning will likely cure any intermittent operation. The most durable cleaning process is a two step operation. First, squirt a little solvent-type cleaner (such as Caig Labs CaiKleen 41 or Chemtronics Electro-Wash PX) into the power plug. Then insert the plug into the jack on the codec, and rotate the plug to wipe the contacts. Now remove the plug and squirt some Caig Labs DeoxIT into the plug, and repeat the wiping process. The DeoxIT coating will last quite a while, so you shouldn’t have to do this very often.

Q. I am going crazy trying to dial (HotLine, Matrix, BlueBox) calls with an external phone. The modems just keep whining. What am I doing wrong?

A. I won’t make rude comments about the modem imitating its owner but rather suggest that this is probably only an issue about timing. We recommend that you get the codec ready before dialing by bringing up the screen instructing you to dial with an external phone. Dial the call on the phone, and as soon as you hear the first ring, press enter on the codec and hang up the phone right away. Don’t wait until the modem at the other end answers, or the off-hook phone will become part of the negotiation. Also please note that the Matrix and BlueBox can take a 44 digit dialing string without the need of an external phone. The same is true of Vectors and HotLines with current software. If you have an older Vector or HotLine that won’t do this, contact us for the free upgrade.

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

TechTip: Mobile Phone Interfacing 101

Most of what we do involves improving the audio of telephone calls, but we often get requests for technical information about interfacing to mobile phones without any audio processing. The easiest way to do this is to connect your audio source through a hands-free port on the phone. So here’s a short technical primer on typical hands-free mobile phone connections.

Most Motorola phones present a 3-conductor 2.5 mm jack as a hands-free port. Many third party hands-free headsets use this connector and adapters are available for other brands to a 2.5 mm jack. The jacks are wired so that connector “tip” is audio going into the phone, “ring” is audio out of the phone, and “sleeve” is ground (as shown). Care must be taken because these signals are biased by a DC voltage, so input and output audio signals must be AC coupled to the phone. Because you can’t be sure about input and output impedances of any particular phone’s hands-fee port, it’s best to use fairly large-value coupling capacitors (1uF or higher, in order to avoid limiting your frequency response into the mobile phone).

Plug Drawing

On our phones, we found suitable send levels (into the phone) in the –45 dBu range, and typical receive levels (out of the phone) of about –20 dBu. Obviously you’ll need to adapt any field mixers and headphone amps to these levels to avoid over/underdriving your gear.

Comrex’s New Headquarters - We’re moving!

New Building

We are SO excited! Thanks to our loyal and valued customers like you, we are in the position of having outgrown our present facility. So, we are building a new home for Comrex. We have chosen a site in Devens, MA (the old Fort Devens military base) which has reinvented itself to become the hottest new technology and development campus in the area. Our building is well under way, and we are planning to move shortly after NAB at the end of April [NOTE: We are now moving June 1, 2002]. Please make a note of the change of address [19 Pine Street, Devens, MA 01432] and phone number [978 784 1776] for your files. Of course you can always find us on the web at www.comrex.com.