Reader Feedback

It sounds like a Rube Goldberg, but it worked flawlessly.

Dear Don,

I thoroughly enjoyed your article on UPS and emergency power systems in the latest issue of BE. I was Director of Operations at Radio Free Europe from 1985 to 1995. Our entire Munich studio plant was rebuilt during that time, and the new facility included an electromechanical UPS from the Dutch firm Holec. This thing had a 400kva generator driven by an electric motor with a big flywheel to provide energy storage. When the city power failed, the drive motor would unclutch and a diesel engine would kick in and pick up the load.

It sounds like a Rube Goldberg, but it worked flawlessly. It was even delivered in its own insulated enclosure, ready for setting on a concrete pad. It had a very elaborate muffler system to keep the peace with the neighbors, too. The only indication of a power failure inside the building was a red light in the IT network center that let you know the diesel was running. The diesel had a synchronizer that would phase it up with city power when it came back on, so the transition back was glitch-free as well. The Holec ran the studios (all 30 of them) plus the transmission center and the computer center, which was huge (the third-largest VAX cluster in Europe). We had a pair of Mercedes Benz 300kva generators to run everything else. Very German and very reliable. We ran the system under load for at least one hour every week, and it ran for a minimum of half an hour whenever it started in an emergency. If memory serves, we didn't switch back to city power until it had been stable for at least 15 minutes after returning.

I've never seen an electromechanical UPS in this country, but I assume they must be out there somewhere.

I always enjoy your column. Keep up the good work.

Best regards,
Wilson Louis Brown
Integration Project Manager
EMC Media Group

Don Markley responds:


First, thanks for the kind words. Second, I find your comments concerning the big flywheel system interesting. In my own little hometown of Peoria, IL, Caterpillar is making, or at least marketing, such a system coupled with their generators. One of my clients had mentioned the possibility of using one of these systems rather than a big UPS to power their new transmitter plant — two transmitters and associated goodies. Together we had sort of dismissed the concept as a bit too Rube Goldbergish in accordance with your thoughts. Now, based on your comments, we are investigating it further. It may be the same system you used, as Cat now has very close relationships with several German firms. For example, they make a combine where a German company manufacturers the machine, and Cat furnishes the engine and markets it in the United States. Thanks for the information on its performance and reliability.
Don Markley

Capturing closed captioning

To Brad Gilmer:

I just read your article on titled “Interactive television for terrestrial broadcasters.” It was a helpful description for me, and I was wondering if you had a few minutes to point me toward more detailed information.

I've been asked to look into writing software that will capture and interpret the streams of data that are available on VBI-Line21 (all the CC and Text fields). Is there an Internet site that details the formats of the data on these fields, and any chance there's an existing Windows-based COM control that would provide me the data?

Thanks in advance,
Steven Crawford

Brad Gilmer responds:

Dear Steve:

You are in luck. There is a standard published by the Electronic Industry Association (EIA) that describes closed captioning in all of its various forms. The standard is EIA-708B, and is titled Digital Television (DTV) Closed Captioning.

You can order a copy of the standard from EIA through their distributor, Global Engineering Documents (GED). The website for GED is Enter EIA 708 in the Document Number Search field.

Brad Gilmer

Length does matter

To Michael Robin:

What is the practical length of a 75Ω coax cable for AES/EBU applications before the signal can't be regenerated?
Jim McCann

Michael Robin responds:

Dear Jim:

Current technology allows the safe use of up to 1000 meters of 75Ω coaxial cable for the distribution of AES/EBU digital audio. This assumes, of course, that the cable is properly terminated at both ends to avoid standing waves, which result in unpredictable performance.

Michael Robin