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	Ringdown
		Ringdown: In telephony, a method of signaling an operator in which telephone ringing current is sent over the line to operate a lamp and cause the drop of a self-locking relay.
		Note 1: Ringdown (a) is used in manual operation, as distinguished from dialing, (b) uses a continuous or pulsed ac signal transmitted over the line, and (c) may be used with or without a switchboard.
		Note 2: The term "ringdown" originated in magneto telephone signaling in which cranking the magneto in a telephone set would not only "ring" its bell but also cause a lever to fall "down" at the central office switchboard.
	www.ebroadcast.com.au /lookup/encyclopedia/ri/Ringdown.html (112 words)

	Photonics.com Printer Friendly Article
		In recent years, investigators have adapted the principles of ringdown spectroscopy (see sidebar, facing page) to fiber optic configurations by placing high reflectors on each end of a fiber and observing the ringdown time of an injected pulse.
		With the loop gain clamped, the researchers observed ringdown times as long as 200 µs, although they note that repeatability of these long times was difficult.
		The longest ringdown times occurred when the laser was tuned to the same frequency as the injected pulse so that both passed through the filter with minimum loss.
	www.photonics.com /printerFriendly.aspx?contentID=77496 (613 words)

	Title
		Cavity ringdown spectroscopy has been applied to hydrogenated amorphous silicon (a-Si:H) showing that this fully optical method is suited for the detection of defect-related absorption in thin films with a minimal detectable absorption of 1x10(-6) per laser pulse and without the need for a calibration procedure.
		We have developed a variant of cavity ringdown spectroscopy for the mid-infrared region between 9 and 11 mu m, exploiting the intracavity power buildup that is possible with continuous-wave lasers.
		We have investigated the applicability of the cavity ringdown technique in the millimeter wave region, which is rich in the rotational spectra of molecules.
	www.tigeroptics.com /PAGES/CRDS.htm (19209 words)

	Ringdown - Wikipedia, the free encyclopedia
		In an application not involving a telephone operator, a two-point automatic ringdown circuit, or ringdown, has a telephone at each end.
		In some cases, automatic ringdown circuits have one-to-many configurations.
		When one phone goes off-hook, a group of phones is made to ring simultaneously.
	en.wikipedia.org /wiki/Ringdown (618 words)

	State Water Resources Research Institute Program
		In the second scenario, the use of cavity ringdown in spheres might only result in sensitivity comparable to laboratory-based methods, but might be amenable to field use.
		In our experiment, the cavity ringdown is achieved through the total internal reflection of the light beam on a spherical surface which also serves as the focusing device.
		The high reflectivity is guaranteed as long as the index of refraction of the sphere is greater than that of the surrounding medium and the angle of incidence is greater than the critical angle.
	water.usgs.gov /wrri/00grants/TNspectro.html (2120 words)

	Gernot Friedrichs - Research (Site not responding. Last check: 2007-10-13)
		A requirement for a simple quantitative measurements of concentration-time profiles by means of CRDS is a (quasi) steady concentration of the detected species during the whole ringdown (typically several tens of μs).
		In this case, the concentration of the species can be easily extracted from the single-exponential ringdown time constants by pump-probe schemes with variable time delays between photolysis (pump) and ringdown (probe) laser pulses.
		For "fast reactions" that occur on the same time scale as the ringdown, the ringdown becomes nonexponential due to the convolution with the concentration change caused by the reactions.
	www.uni-kiel.de /phc/ags/temps/gfriedr/researchtext02.html (443 words)

	September 2000 Highlights
		Current efforts using cavity ringdown spectroscopy for the detection of dioxins are focused on developing the spectral database necessary to construct a dioxin monitor.
		Diode laser cavity ringdown spectroscopy (CRDS) was utilized to investigate the effects of placing an inductively coupled plasma (ICP) in a ringdown cavity.
		A paper entitled "Recent Progress in Analytical Atomic Cavity Ringdown Spectroscopy" was presented at the Federation of Analytical Chemistry and Spectroscopy Societies Conference, Nashville, TN, September 24 - 29, 2000.
	www.dial.msstate.edu /monthlies/sep00.html (1377 words)

	SWIR
		If an absorbing species is placed within the cavity then its presence will increase the overall loss within the resonator and the rate at which the stored light is lost will increase (i.e., the ringdown time will be faster if an absorber is present compared than if no absorber is present).
		In order to test the sensitivity of our SWIR cavity ringdown instrument the absorption spectrum of a dilute mixture of ammonia (NH3) was measured.
		The resulting concentration based on the two lines is slightly different and could be the result of inaccurate values of the linestrengths for the absorption features.
	infrared.pnl.gov /SWIR.htm (449 words)

	LOS GATOS RESEARCH HOME PAGE
		The major limitation in these early approaches was that the coupling of narrow frequency modes between the laser cavity and the ringdown cavity was somewhat chaotic because the two cavities could drift independently.
		Because the injected intra-cavity energy built up slowly over many microseconds, the ringdown cavity acted as a classical etalon and the optical buildup was very irregular as the cavities drifted in-and out of resonance.
		First, by using a laser pulse shorter than the ringdown cavity round trip length, we could avoid the spiking amplitude noise resulting from the strong interference effects of a spatially overlapped coherent light beam within the ringdown cavity.
	www.lgr-home.com /crd.html (1113 words)

	Novel Trace Gas Detection Techniques With Quantum-Cascade Lasers
		After the cavity is filled with radiation, the laser emission can be interrupted and the ringdown decay measured in the same manner as it is done with a pulsed laser.
		This triggering-and-acquisition process is repeated and consecutive ringdown transients are stacked in the A/D memory until a desired number of transients is acquired.
		An inverse ringdown time plotted as a function of the laser current provides the absorption spectrum.
	www.isso.uh.edu /publications/A2001/105-harman.htm (2730 words)

	Division of Information and Communication Sciences
		The Centre for Lasers and Applications (CLA) is at the forefront of research into the development of lasers to 'sniff' diseases on a person's breath.
		When the laser is shut off, the 'ringdown' or decay rate of the light leaking from the cavity provides information on the exact composition of the gas.
		Orr and He have applied to patent an innovative cavity ringdown spectroscopy device which uses very small lasers developed for the telecommunications industry, and believe a prototype could be built at about the size of a small suitcase.
	www.ics.mq.edu.au /industry/innovation (984 words)

	Synopsis
		is the central frequency of the ringdown waveform and
		For a fl hole ringdown, the gravitational waveform produced, averaged over the various angles, is
		where the central frequency and quality of the ringdown are determined from the mass and spin of the fl holes.
	www.lsc-group.phys.uwm.edu /lal/lsd/node2740.html (188 words)

	Gernot Friedrichs - Research (Site not responding. Last check: 2007-10-13)
		In this case, the concentration of the reactive species remains almost constant during the ringdown period and complete concentration-time profiles can be obtained from the single-exponential ringdown time constants by pump-probe schemes with variable time delays between the photolysis (pump) and ringdown (probe) laser pulses (see also here).
		In this case, rate constants can be extracted from the nonexponential ringdown signals by the simultaneous kinetics and ringdown (SKaR) model developed by Brown et al.
		In this case, different frequency components of the probe laser light in the ringdown cavity experience different absorptions and thus decay with different time constants.
	www.uni-kiel.de /phc/ags/temps/gfriedr/researchtext08.html (323 words)

	January 2001 Highlights
		The high vacuum system for the diode laser cavity ringdown experiment was completed in January.
		Although the ringdown measurement works wells even at atmospheric pressure, a very low baseline pressure is needed in order to introduce very small partial pressures of volatile organic compounds (VOCs).
		Uranium has been detected using cavity ringdown spectroscopy on both neutral and ionic absorption lines in an inductively coupled plasma.
	www.dial.msstate.edu /monthlies/jan01.html (1644 words)

	Ringdown Spectroscopy (Site not responding. Last check: 2007-10-13)
		Cavity-enhanced spectroscopic methods have redefined the sensitivity limits of direct absorption spectroscopy.
		The most well-known of these techniques, cavity ringdown spectroscopy (CRDS), offers direct absorption measurements with laboratory sensitivities as low as 8.8 × 10
		However, most of these highly sensitive instruments based on cavity-enhanced spectroscopy require actively locked cavities, high degrees of vibrational isolation, and extremely fast detection electronics [Ma et al.
	www.arp.harvard.edu /kinetics/sciobj/freerad/expmethods/ringspec.html (302 words)

	Proctor automatic ringdown, line extender telephone products
		The unit features user-selectable one-way or two-way ringdown operation and three different ringing patterns.
		The 46220 is ideal for facilities requiring immediate uninterrupted communications, such as military bases, emergency service centers, entry gates and guard shacks, school campuses, hotel/motel complexes, retail stores, large business offices and private residences.
		The user simply plugs the unit into the nearest standard AC outlet, plugs in the line cords of the two telephones, and lifts the handset of one phone to automatically ring the other.
	www.proctorinc.com /46220.htm (377 words)

	webpage (Site not responding. Last check: 2007-10-13)
		An exploratory study of cavity ringdown spectroscopy as a noninvasive breath diagnostic for breast cancer DOD DAMD17-03-1-0757 $200,215.
		Cavity Ringdown Spectroscopy Symposium (organized by Richard Saykally) 27th FACSS Conference Nashville September 24-28, (2000).
		D. Wagner, C. Winstead, and G. Miller "Infrared Cavity Ringdown Spectroscopy", in Handbook of Vibrational Spectroscopy, J.M. Chalmers and P.R. Griffiths (Eds), John Wiley and Sons, Ltd, Volume 1, pp.
	www.personal.utulsa.edu /~george-miller (565 words)

	ICOS Can Measure Exhaust Emissions in Real Time on Real Vehicles
		The time required for the pulse intensity to decay to a specified proportion of the initial intensity is called ringdown time.
		Because a ringdown profile and measured ringdown time is generated for each laser pulse, fluctuations in laser pulse energies from shot to shot do not affect the accuracy of the measurement.
		The ringdown time indicates the concentration of the specified gas in the sample.
	www.ornl.gov /sci/eere/state_partnerships/ICOS.htm (473 words)

	Guardian Telecom Waterproof 4X Phone (Standard & Ringdown Versions) - Guardian Telecom WP80 - TWAcomm.com, Inc.
		Guardian Telecom Waterproof 4X Phone (Standard andamp; Ringdown Versions) - Guardian Telecom WP80 - TWAcomm.com, Inc.
		Guardian Telecom Waterproof 4X Phone (Standard and Ringdown Versions) (Discontinued)
		The sturdy urethane enclosure protects the internal circuitry against wind blown dust and rain, corrosion, splashing and high pressure water.
	www.twacomm.com /catalog/model_WP80.htm (296 words)

	CDW Product Overview: Viking DLE-200B Emergency Telephone Ringdown Circuit
		CDW Product Overview: Viking DLE-200B Emergency Telephone Ringdown Circuit
		This product has been discontinued as of Wednesday, November 22, 2006.
		Provide details about why you like or dislike the product.
	www.cdw.com /shop/products/default.aspx?EDC=450095 (220 words)

	2 Way Ringdown Circuit
		Allows communication between 2 devices * Provides sales people with a cost effective method of conducting on-site demos * Telephone line simulator for trade show demos or customer site.
		* provides standard (2 sec on, 4 sec off) or custom 20 HZ ringing/32 V talk battery * Provides communication between virtually any 2 telecom devices including: Ringdown applications between elevator/emergency phone or phone systems
		The 1950's Pay Phone is now available in a new Hot Pink color.
	www.payphoneoutlet.com /vik-dle-200b.html (186 words)

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