Doing more with less; that's the name of the game in broadcasting today. As revenue dollars shrink, I don't have to tell you how it affects the size and expertise of your technical staff. Running an efficient remote engineering department is becoming more of a challenge. Equipment needs to be flexible, yet easy enough for employees with entry-level skills to operate.
I had the opportunity to examine the features and functions of the Zephyr Xport from Telos. In short, the Xport is a full-duplex mono audio codec to send audio via POTS or ISDN. The unit is designed to communicate with its companion, the Telos Xstream ISDN studio unit. The Xport can use the new MPEG AAC-LD coding at a 64kb/s rate.
The Xstream ISDN studio unit automatically detects when the in-coming call is POTS or ISDN and configures itself accordingly. To communicate with other ISDN units the Xport can be configured to transmit with G.722 encoding. I found that the MPEG AAC Plus low bit-rate encoding delivers superior quality down to 16kb/s using spectral band replication techniques.
Performance at a glance
20Hz to 15kHz audio over ISDN and POTS
Automatic phone coupler backup
AAC Plus encoding
Integrated mixer and multi-band AGC/limiter
Remote control via Ethernet
Computer audio streaming via Ethernet
ISDN line sharing
Ancillary dry contact closures
Think of this box as the Swiss Army knife of remote equipment. It includes a mixer with one microphone and one line-level input, as well as a headphone local/remote mix and volume control. Telos has incorporated an Omnia multi-band digital AGC/limiter on board. You can tell that the designers at Telos are thinking of us in the field with stowable control knobs that tuck neatly into the front panel. Set the level, press the knob in and you're ready to go. No more accidental bumps to knock you off the air.
Configuration, dialing and signal monitoring can be observed on the front-panel LCD display. Instead of showing you a static data rate screen, the Xport displays a line quality bar graph for incoming and outgoing data streams. Status prompts inform the user of modem activity such as off-hook, connecting and renegotiation request. The design is clean and simple with just a few navigation buttons. Of course, there are manual-dial and speed-dial buttons as well as 100 memory dial locations. The Xport's built-in power supply will accept voltages from 100Vac to 240Vac.
The Xport uses a custom-designed modem as opposed to a standard off-the-shelf variety modem to achieve a robust data stream. The Xport will work under the most difficult of line conditions. In the event that line quality goes to pot (no pun intended) the Xport will revert to a phone-line quality mode so the show can go on.
Throughout North America, two-wire U ISDN service is used. Four-wire S ISDN service is used elsewhere around the world and in parts of the United States and Canada. The Xport is equipped with RJ-style jacks to accommodate both formats. Thirty location setups are provided to store SPID or MSN numbers. I like the fact that two Xports can share a single ISDN to achieve two-channel audio when needed. When landlines are unavailable or impractical, a cell phone jack is provided on the back for phone quality audio over wireless telephone networks.
Detail of the screen showing audio metering and connection quality.
An Ethernet port on the rear panel allows connection between the Xport and a PC. If the Telos Soundcard Emulator driver is loaded on the PC, it can stream audio from the computer back to the studio. Remote control is accessed through the Ethernet port using a standard Internet browser. Other features include dry contact closures for remote starts/stops and auxiliary audio outputs for recording.
Down on the farm
When the field test Xport arrived, I was impressed with the sleek stainless-steel look, but I wondered if the audio quality would match this look. On the bench, the Xport performed with jaw-dropping clarity in the POTS AAC Plus mode. This was fine in the studio test, but I needed to see it in action in the field.
My opportunity to field test the Xport came when one of our morning-show announcers took maternity leave. Being the trooper that she is, she was prepared to work the show from her home studio right up to the last minute. This was my chance to test the Xport under real-world conditions. We had no idea how hard this task was going to be.
Not only does this announcer love country music, she also loves the country. Her home and studio are in rural Missouri nearly 60 miles from our studios. An RPU shot was out of the question because of the terrain. I turned to ISDN, but the telephone company that promised the ISDN service backed out within a week of our first remote broadcast. Our only remaining option was POTS.
We successfully connected the first time with amazing results (considering the age and distance of the copper through which this signal traveled). The Xport had to negotiate to a low rate to work over the poor lines. We had a little delay because of the low data rate, but the host was able to keep up with callers and her sidekick on-air. It wasn't an ideal solution considering the circumstances, but we were able to pull it off thanks to the Xport.
The Xport lacks a direct way to read connection speed. Personally, I like to know in discrete terms what my line quality is. Another negative for me is its lack of operator control over rate renegotiations, but I can understand the need to automate or mask such operations so as not to confuse operators.
If you're considering the purchase of an Xport, keep these things in mind. You must own a Telos Zephyr Xstream ISDN studio unit. It must have software version 2.5 or greater. Software upgrades for the Xstream are free.
The author of the operator's manual alludes to the fact that the AAC Plus algorithm is open to everyone to license and use. His hope is to encourage standardization and interoperability among vendors for the sake of the customer. History has proven that companies who share knowledge tend to be survivors unlike past blunders like Betamax and Mac computers.
Chestnut is assistant chief engineer at Entercom Kansas City.
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