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Č. 31/2014 (06.10.2014)
Invisibility for everyone.
Inspired by fairy-tale stories about invisibility cloak, researchers around the world repeatedly attempt to create something that could hide people and objects from the eyes of others, even if to a limited extent. They have been trying to use both simple methods as well as those based on the latest technology. The last attempt made by scientists at the University of Rochester (USA) seems to be a breakthrough. Firstly - the result is much better and without certain limitations characteristic for the previous solutions, and secondly - the effect of invisibility was achieved by using ordinary, readily-available optical lenses. Interestingly, everyone can try to build their own "cloak" - it's enough to read this article to the end...The system is based solely on optics and mathematics. By arranging two pairs of lenses in a special way, it is possible to bend the light in such a way to hide anything that will be in the middle of the structure. The larger the lenses, the bigger items can be hidden. An important fact is that the effect of invisibility is obtainable when the viewer is looking at an angle greater than 15 degrees with respect to the main optical axis, otherwise the phenomenon does not exist - contrary to previous solutions.
The obvious application of this solution is camouflage, but for an effective use is is necessary to build advanced optical systems, especially in the case of moving objects. According to the researches, Joseph S. Choi and and John C. Howell, "in addition to hiding an object, these cloaking devices can also make an object behind a barrier visible, or deflect light rays." So, they can be used for elimination of dead zones on vehicles, or for the increase of the field of view of surgeons during operations.
Dr. John Howell decided to spend holidays with his son to build "invisibility cloaks" from widely available materials. The effects of their work can be seen in the video. The entire cost of the "fairy stuff" was 150 USD.
How to create your own cloak - instructions:
1. You need two sets of lenses with different focal lengths
(f1 - e.g. 200 mm, f2 - e.g. 75 mm)
2. The distances between the lenses should be as follow: t1 = f + f2, t2 = 2 * f2 * (f1 + f2) / (f1 - f2)
Notes:
(f1 - e.g. 200 mm, f2 - e.g. 75 mm)
2. The distances between the lenses should be as follow: t1 = f + f2, t2 = 2 * f2 * (f1 + f2) / (f1 - f2)
Notes:
- Achromatic lenses give the best picture quality
- Fresnel lenses can reduce the total length of the system
- The shorter the system, the greater the range of invisibility and edge effects less noticeable
TERRA amplifiers and modulators - versatility and professionalism.
The devices of the at4xx series provide a system solution for shared antenna systems (MATV), with gain adjustment and interference reduction. They are also used in SMATV systems. The at420 R82510 / at440 R82511 amplifiers with stabilized output level of about 80 dBμV are ideal for equalization of DVB-T channels before injecting into multiswitch system. The mt-420 R82515 / mdx-420 R82518 modulators allow for integration of the antenna system with video surveillance, distributing the "security channels" in analog or digital form. This increases security and helps to protect the property of the residents.
Ultra selective SAW (Surface Acoustic Wave) filters strongly reduce interference (selectivity 40 dB at -/+2 MHz from channel borders). With this feature, TERRA channel amplifiers are particularly appreciated in very difficult reception conditions.
A set of TERRA channel amplifiers and modulators will ensure high quality reception and reliability of the system for many years. The devices of the at4xx series form a comprehensive solution for shared antenna systems. Such a set may include (depending on the needs):
- twin channel amplifier at420 R82510 - for filtering, amplifying and equalizing levels of antenna signals in UHF band (DVB-T),
- four-channel amplifier at440 R82511 for filtering, amplifying and equalizing levels of four DVB-T multiplexes,
- broadband amplifier ma400 R82520,
- twin VSB multi-standard modulator mt420 R82515,
- twin DVB-T modulator mdx420 R82518,
- accessories (power supply DR-60-12 R82532, installation hardware etc).
PoE switches - the easiest way to power network devices.
Modern IP systems can be much easier implemented with the use of PoE technology (Power over Ethernet). The best PoE solution seems to be the integration of switching and powering functions, i.e. the application of switches with PoE functionality.Main features of PoE technology:
- transmission of power and data via a single cable reduces wiring and installation costs
- range at least of 100 m (with appropriate cabling)
- high security and and reliability - in typical conditions the risk of electric shock is not high (the voltage is below 60 V) and the technology involves auto-testing procedures
- protection of devices not compliant with the standard
- ease of installation
ULTIPOWER 0288af PoE managed switch ensures smooth connectivity in 10/100/1000 Mbps Ethernet networks. It has 8x RJ45 10/100 Mbps PoE ports supporting Auto-Negotiation function, RJ45 1000 Mbps port for connecting to access network and 2x SFP 1000 Mbps ports allowing for integration with optical networks. The 8 PoE ports automatically detect PD devices compliant with IEEE 802.3af standard and provide them with power supply. This feature allows the user to expand the network coverage in areas where there is no access to AC power lines/outlets and to employ access points, IP cameras, IP phones, etc. Two SFP slots allow for integration of the switch with an optical network.
Optical fibers in installation boxes.
The transition from copper to fiber optic systems may seem difficult for many installers of low voltage systems. The habits resulting from the experience gained by many years of practice with copper systems often turn out to be a big problem in the case of optical networks. One of the fundamental skills that any FTTx installer must develop, is the due diligence in arranging optical fibers. This applies to running cables through wells, walls, conduits and protective pipes, and their termination in distribution frames and installation boxes. The latter task is usually the most difficult one.Distribution frames and installation boxes for fiber optic systems are designed to simplify the work of the installer as much as possible, while maintaining good organization of the cables and fibers. Each of the distribution/termination boxes has three distinctive elements: a place for the incoming and pigtail fibers, an area for protecting splices, holders for adapters.
The diagrams above show an example of organizing fibers and installation components in the Ultimode TB-04B-2 L54041 box. The incoming cable enters the box through the cable fitting with the largest cross-sectional area. The fitting protects the cable against moving, by screwing down the carrier component - a tube, sheath or rod - to the body of the box. Fibers, passing under the tray, run through a dedicated hole. The tray keeps reserves of the fibers, and splices which are fixed to prevent rotation. The excess of the pigtail fibers is also stored on the tray, and their sections are led through a hole by the hinge of the tray to adapters inserted into the holders.
Regions Of Interest (ROI) in Hikvision IP cameras.
Hikvision IP cameras of the DS-2CD2xxx series with firmware version v.5.2.0 or higher have been equipped with additional video-analysis functions. One of them is ROI (Region Of Interest) function. This function "extracts" part of the image which should be transmitted with a higher quality than the rest. Typically, the fragment is particularly important from the point of view of surveillance purposes and thus it imposes higher requirements for image quality.The use of the ROI function is recommended in the case of links with bandwidth insufficient for the transmission of the whole image in the highest quality. Thanks to this function, the most important piece of the image contains all the necessary details, whereas the remaining part is more compressed .
In the current version, the user can activate one region in the main stream and one in the secondary stream. The image quality of the regions can be independently adjusted within the range of 1 to 6 (the higher number the higher quality).
IP CCTV systems - recording of surveillance data when the LAN fails.
IP CCTV systems require the highest possible degree of protection of the surveillance data. Professional monitoring systems where the priority is their reliability ensure variety of security features that are designed to provide trouble-free operation, regardless of the circumstances. In the event of an NVR failure, the data can be recorded on a redundant device. In the case of LAN breakdown, the material can be recorded on micro-SD cards installed directly in IP cameras. They record the video streams that cannot reach the NVR because of the network failure.
The series of low-cost Hikvision DS-7600NI-SE NVRs plus Sunell IP cameras equipped with GOODRAM memory cards enable the users to cut the costs of IP CCTV systems while providing distributed backup of the surveillance data in each camera. All Sunell IP cameras can locally record the data on the SD cards. The Hikvision NVRs can notify the system operator about LAN failure e.g. by a sound alarm.
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 | Wireless Access Point RouterBoard SXT-5HPnD N24115 is a complete device of the Customer Premises Equipment (CPE) category, compliant with 802.11n standard. It operates in 5 GHz band using MIMO 2x2 technology, has double-polarization antenna with 16 dBi gain and separation between the polarizations of 35 dB. The RouterBoard SXT-5HPnD access points usually operate as client stations and can also be used to build point-to-point links. |
News
Sept. 30, 2014 - new training session in DIPOL. The free trainings is Poland will cover new subjects such as practical configuration of IP CCTV systems and issues connected with F&Home RADIO system for intelligent homes and buildings. Other subjects will include designing of SMATV and fiber optic systems in new buildings in accordance with regulations introduced in Poland about two years ago.
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