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Technology Stocks : The *NEW* Frank Coluccio Technology Forum -- Ignore unavailable to you. Want to Upgrade?

To: NDBFREE who wrote (24785)	1/4/2008 12:03:01 PM
From: Frank A. Coluccio	Respond to of 46821

Hi Joe. re: "Believe for future data centers more thought will be given to building all DC data centers with the power used generated by gensets, etc. powering DC (not AC) electric generators." It certainly would help matters if more data center equipment manufacturers (servers, mainly) were to adapt their gear (or, if customers would specify the delivery of said gear) to accept native d.c. at appropriate levels, as opposed to taking in mostly 110vac at every rack and chassis, often multiple a.c. power lines for redundancy, and then undergoing the inefficient conversions you cited. Otherwise, distributing native d.c. from the power closet (power distribution unit) to racks and cabinets goes nowhere. re: "Don't believe it is possible to build a DC power transformer." I'm not sure if you've asked a question or voiced what was once perceived to be the case during the late nineteenth century, but d.c. can be stepped up, effectively, many times. You may recall the power packs that photogs once (still?) wore on their belts to power their electronic flash units (flashbulbs). I once taught the principle of operation and repair of these units to US Army Signal Corps repair depot personnel. Essentially, a 9 volt d.c. battery was fed through a then-electromechanical (today-semiconductor) vibrator (inverter), thus creating an on-off current simulating a form of a.c. The a.c. was, in turn, passed to the primary stage of a 1:100 step-up transformer and then through a rectifier yielding 900 vdc across an electrolytic capacitor or condenser rated for 1,000 vdc. The capacitor held the charge until the photographer pressed the flash button, and then the charge process would begin again immediately. (As an aside, these capacitors, when charged to the full 900 vdc, worked great on warm, lazy days when students were observed nodding or dozing off to sleep. By discharging one of these across an aluminum chalk ledge in the front of the room, one could effect a loud, cracking boom sound (ka-bang!) like an M-80 going off. It's not the best way to make friends, I'll grant you, but it sure helped in regaining everyone's attention.) In the foregoing example, the low voltage d.c. was first converted to a.c., then stepped up 100 times, and then converted back to d.c. at a much higher voltage. ------

To: NDBFREE who wrote (24785)	1/4/2008 5:11:25 PM
From: Frank A. Coluccio	Respond to of 46821

Crossing the deep divide: Improving wireless cell site backhaul in the last mile By Peter Neill, Level 3 Communications Lightwave \| January 2008 [FAC: Hi Joe. I'm directing this article to you because you once inquired about the subject of wireless backhaul preferences. Actually, I've received queries from quite a few netizen friends inquiring about wireless backhaul prospects, given the niche's potential market size. Enjoy!] Evaluating coverage, price, performance, and time-to-market, it is clear that hybrid fiber/wireless networks meet the immediate backhaul needs of wireless service providers. During the past 15 years, mobile phone usage has skyrocketed. What initially started as a voice services phenomenon is now exploding into a worldwide hunger for both traditional voice and next-generation broadband data services. Where wireless service was once a luxury, it has now become a critical part of everyday life for billions of subscribers. Consumers that were previously happy speaking with their friends and family via telephone are clamoring for "anytime, anywhere" wireless access to movies, music, television, and mapping- and location-based devices. Cell phones—which once included only basic telephony functionality—have morphed into multipurpose mobile devices. The booming demand for next-generation wireless services, combined with the steadily rising consumption of subscriber minutes and increased data requirements presented by demand for larger file multimedia content, has exponentially increased the backhaul requirements of cell site locations. These factors are driving up expenses for wireless operators, cutting into profitability and putting pressure on margins. Wireless providers, who have been relying on legacy copper infrastructure for more than a decade, have acknowledged that copper is not a scalable option for supporting next-generation wireless requirements or reducing backhaul expenditures. Leased lines not only create network performance issues and lack scalability, but they are also expensive, costing several hundred dollars per line and accounting for nearly 30% of provider operating expenses. So what can wireless providers do to meet the growing needs of subscribers while simultaneously improving profitability? Efficient, reliable backhaul is the key. Weighing the options Cont.: lw.pennnet.com Author: As senior vice president of wholesale offer management for Level 3 Communications (www.level3.com), Peter Neill is responsible for Level 3's wireless, domestic and international carrier, and system integrator businesses. ------

To: NDBFREE who wrote (24785)	1/5/2008 6:27:47 AM
From: axial	Respond to of 46821

Joe, thanks to you and Frank for your replies. The subject turns out to more complex than it appeared - but I'm getting used to that, on this thread ;) Jim

To: NDBFREE who wrote (24785)	10/20/2009 11:06:03 AM
From: Frank A. Coluccio	Read Replies (1) \| Respond to of 46821

[Free-Space Optical] Tech Questions Worth Repeating concerning FSO testing, from the Fiber Optic Association Newsletter of 10-19-09 thefoa.org Scroll down to: "Good Question! Tech Questions Worth Repeating" Free-Space Optical Q: We are connecting two buildings which are about 15 KM apart.We cannot lay fiber cable under ground due to government regulations. On microwave we can only get 100Mbps. I am pondering the use of optical over the air. Kindly advise if this would be appropriate for this link. A: Typically, line of sight optical systems are limited to about 2 km distance but can be repeated for longer distances. They are susceptible to interruption by fog, rain, even birds flying through the line of sight, so may not be appropriate for your application. Q&A continues at URL above. ------