User Reports
You Can Perform Magic On A Pots Line!
by Greg M. Savoldi
Director of Engineering-Columbus-Jacor Broadcasting
We've used ISDN circuits in this market for about four years. Initially, it took a Network Interface (box #1), the Terminal Adapter (box #2), the Codec (#3), and the outboard mixer (#4!) Shove all of this stuff into a 'custom' rack kit that could fly the friendly skies (with not so friendly baggage handlers!), and you could get some great audio to/from most "large" cities in the country. The phone company needed several weeks of lead-time, and after some start-up jitters, we could generally get a bearer channel talking and do 10K of bi-directional audio. WOW! Seems like a lot of hassle, but in its time, this was cutting-edge digital!
Today, ISDN is probably available at your home (and many use it daily!), the technology and service is very affordable, plus the reliability is good. Codecs have graduated into 'all-in-one' machines that are literally plug-n-play. Add a mic and headphones and you're up. But you still have to order the ISDN line, and even Ameritech's best turnaround is about a week. Usually not a problem for those 'planned' remote venues. We do a lot of them in the Columbus market, plus take daily feeds from our sister Jacor markets for many programs. (Four ISDN circuits are currently on-line at our Dublin Road facility alone.)
But you need it NOW! The late-breaking story 50 miles out of town(beyond an RF shot). The 'roving reporter' situation, as he follows the President, the spring training camp updates, the one-day 'drop-ins' from Anytown Earth. You need fast, simple, reliable, and good quality. As my sports director says, ...."if ya don't send an engineer, then it's gotta be moron-proof!" OK, consider it done. Comrex's HotLine is the answer to every non-technical person's nightmare, and every engineer's magic box!
Here's a unit that can give you up to 10KHz bi-directional audio over a standard 1 MB(POTS) phone line! Really? Well, let's go through the above-mentioned criteria and see how it scores.
FAST: Got a fax machine line you can 'borrow' for a while? "Hello? Anybody home?" Borrow a line at a residence (carry a fresh station T-shirt at all times as a way to say THANKS!) Anywhere you can grab 'tip and ring', this bad boy is ready to do business!
SIMPLE: Weighs less than three pounds and comfortably fits in a briefcase or softbag. Find electricity, plug the phone line into the RJ-11 jack, and hit Q-DIAL for a preprogrammed 'call the mothership now' button. HotLine will initiate the call, tell you how things are going via its LED/LCD displays (like carrier detection, ringing, negotiation of data flow, etc.), and after about 15 seconds you're ready for air!
RELIABLE: Probably one of the best points of ALL Comrex products (we own many), and the HotLine shines here, too! Beyond all the 'built bulletproof' stuff, this unit will automatically negotiate the best data rate possible to insure a reliable link, free of drop-outs, glitches, digital audio bursts, etc. With a simple selection from the on-board keypad, HotLine will analyze the link you are using, and determine the best compromise of audio bandwidth (frequency response) versus reliable data rate transmission. Let's face it - some POTS lines are better than others! Noisy copper, loaded pairs, slics, PBX switches, aerial pairs, splices, crosstalk, older C.O. systems....it's the real world. Most PBX's and long-distance carriers can handle 21.6kbps (think of this in terms of your PC's modem and your 'average' connect rate). With this speed, you get over 6KHz of good quality audio. Around town (no LD carrier), we can repeatedly do 24kbps, which opens up the audio to over 7khz! As you approach 28.8kbps, you're well into 8K audio, then topping at 10KHz with a 33.6 kbps rate. If needed, the HotLine, can ratchet back to 12kbps, and still provide workable 4.5 audio. Keep in mind you can 'lock' the unit to any rate you wish, which can be helpful in 'unchartered' phone systems where a more conservative/foolproof approach may be desirable.
GOOD QUALITY: HotLine is optimized for speech, but it is no slouch on more complex audio! I gave you the above-mentioned date rate vs. audio response specifications, but 'static specs' don't always tell the whole story. THIS BOX SOUNDS GOOD! Even the 6KHz audio is 'pleasant', meaning most AM stations would sound 'in-studio' with field audio through the HotLine. As always, start with a good microphone. The HotLine provides a switchable on-board mic pre-amp to keep your gear count simple. For users who have a problem with good mic technique and/or expect a wide variance in levels, I advise an outboard mixer with a peak limiter engaged to 'catch' the spikes. (The HotLine has a peak limiter onboard, but I found it a little less than optimum for our applications.)
Real-world test? The 1997 Rose Bowl from Pasadena, CA. Besides three separate ISDN feeds inbound to Columbus, we had "Chuckie," our field reporter, covering the Ohio State Buckeyes around Southern California a full week before the New Year's Day game. Chuckster would simply grab a POTS line, power up, plug in and Q-Dial. We reliably linked at 21.6kbps each time. HotLine provides for a tape input(1/8" jack), so doing wrap-around voicers was a breeze, even for Chuckie! And, did you know you can use the HotLine to repair ISDN circuits? Well, DUH!, but at the Rose Bowl, our ISDN line was not operational at first, but the POTS line was. We linked with the HotLine while Pacific Bell worked out a minor programming glitch on the ISDN. The sports department fed their pre-game tape down the HotLine system, and nobody in programming raised an earlobe!
Drawbacks? It depends on the application. ISDN is still the choice for highest quality, reliability, and lowest digital audio delay time. (the Comrex DXR.1 and NEXUS series work very well on any ISDN duty!) The HotLine gives you good audio (consider you are using a plain old telephone line!) with a tolerable delay time of about 120ms each way. (You will need to generate a simple "mix-minus" from the studio end.) This is the perfect box for spot news, sports, simple remotes, and any 'one-shot' report from the filed. It's the ultimate back-up to satellite and ISDN head-ends for sports networks and such. Where immediacy and simplicity (no engineer required!) are important, Comrex's HotLine is truly the magic box solution.
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