DIPOL Weekly Review – TV and SAT TV, CCTV, WLAN

Undersea fiber-optic cables will help detect earthquakes.

In an article published in the journal Science, researchers from the University of California, Lawrence Berkeley National Laboratory (Berkeley Lab), Monterey Bay Aquarium Research Institute (MBARI), and Rice University have described an experiment that turned 20 km of an underwater fiber-optic cable into a series of 10,000 seismic stations on the ocean floor. During their four-day experiment in Monterey Bay, they detected a 3.5-magnitude earthquake, followed by seismic scattering in an area of underwater fault zones. First tested on terrestrial fiber-optic cables, their method can provide much needed data on earthquakes that occur under the surface of seas and oceans, where they are the most frequent. At the moment, the area, which accounts for c. 70% of the Earth's surface, is practically unmonitored.

The fiber-optic cable used in the experiment belongs to MBARI (Monterey Bay Aquarium Research Institute). The research was conducted by a UC Berkeley graduate and a professor of geophysics at Rice University in Houston. The cable covers a distance of 52 km from the shore to the first seismic station ever placed on the floor of the Pacific Ocean, which was put in place 17 years ago by MBARI and Barbara Romanowicz, UC Berkeley Professor of the Graduate School in the Department of Earth and Planetary Science. The cable itself was only laid in 2009. Because it is currently offline for annual maintenance, a 20 km section was available for use in the experiment.

This is the first time that a subsea cable has been used to detect seismic signals and phenomena. The ultimate goal of the researchers involved in the experiment is to tap the dense network of fiber-optic lines around the world (probably more than 10 million km, both on land and under the sea) as motion detectors to monitor earthquakes in regions that lack costly ground stations.

Image by Nate Lindsey of UC Berkeley

Researchers used 20 km of an undersea fiber-optic cable (pink). During the test, they detected a 3.5-magnitude earthquake, which revealed a previously uncharted fault zone (yellow circle).

The experiment relied on the DAS (Distributed Acoustic Sensing) technique, which is not unlike that used on a daily basis by fiber-optic installers for the purposes of reflectometric measurements. Photonic devices send short pulses of laser light down the fiber-optic line, and the pulse is scattered in the cable. Backscattering is measured by a sensor placed at the beginning of the line. Any anomalies due to cable stretching (e.g. by nanometric tectonic shifts) will modify the strength of the backscattered pulse signal. Thanks to interferometry, scientists can measure the backscatter every 2 m, effectively turning a 20 km cable into 10,000 individual motion sensors.

The experiment has demonstrated that fiber-optic cables can also be used as earthquake detectors. The next step would be to enhance the technique so that existing infrastructure could be used for this purpose without compromising the telecommunications services that it supports.

PoE transmission over 250 m!

The N29978 ULTIPOWER PoE switch (0064afat ) is a desktop device enabling smooth data transmission. It has six RJ45 ports that support speed auto-negotiation, four of which provide power over Ethernet (PoE). The switch automatically detects PD devices compliant with the IEEE 802.3af or IEEE 802.3at standard and provides them with power supply. This feature allows users to expand network coverage in areas where there is no access to AC power lines/outlets and to deploy access points, IP cameras, IP phones, etc. The total power consumption of all connected PoE devices cannot exceed 65 W.

The switch also offers an Extend mode function (activated by a special button on the housing), which allows to power PoE devices connected by twisted-pair cables over distances of up to 250 m. Once the function is enabled, the switch will disable auto-negotiation functions in PoE ports and set a constant transmission speed of 10 Mbps (uplink ports continue to work at 10/100 Mbps).

PoE Switch: ULTIPOWER 0064afat (65W, 6xRJ45 incl. 4xPoE 802.3af/at)
Code: N29978

One cable, two satellite signals.

Using two SAT tuners or simultaneously recording and watching two different channels on PVR (Personal Video Recorder) receivers requires two independent satellite signals. Installations based on SINGLE-type LNBs, dating from several or more than ten years ago, turn out to be insufficient for that purpose

To adapt an older SAT TV installation to support two receivers (or a PVR), replace the SINGLE-type LNB with a TWIN LNB. The additional output of the TWIN LNB has to be connected to the second receiver or the second input of the PVR via another coaxial cable.

Sometimes the installation of the second cable can be very troublesome. In such cases, a good alternative is to apply the R85261 Johansson multi-band converter kit. The kit combines two independent satellite signals and terrestrial FM/DAB/TV broadcasts into one coaxial cable. It is an ideal solution for everyone who wants to replace their simple SAT receiver with a PVR (with two IF inputs), or use another, independent DVB-S/S2 receiver, without having to install another coaxial cable.

An application diagram of the multi-band converter KIT Johansson R85261.
Transmission of two independent DVB-S/S2 signals (from one satellite)
and DVB-T broadcasts via one coaxial cable.

DIN/VDE 0888 fiber-optic cable coding.

The coding and interpretation of fiber-optic cables causes no end of problems for installers and dealers. The difficulty has to do with the complexity of cable codes (usually composed of many letters), the lack of knowledge on how to interpret specific codes, as well as the simultaneous presence of two different coding practices, i.e. the European DIN/VDE standard along with another standard used locally (in Poland, for instance, it is based on the norms of the leading cable producer, Telefonika).

The standard also requires that the name should include two extra pieces of information: core and sheath diameter, as well as the fiber standard. For the cable in question, these figures would be 9/125 OS2, respectively. However, producers often leave out these data.

Cameras with a built-in PIR sensor.

The DS-2CE11D8T-PIRL M75402 and DS-2CE71D8T-PIRL M75398 HD-TVI cameras are fitted with a PIR sensor designed to help detect motion. Classical motion detectors rely on image analysis and may generate frequent false alarms, caused, e.g. by rainfall or branches swaying in the wind. Some may even be sparked by the lack of proper lighting. Every extra alarm consumes disk space and requires users to go over redundant footage. PIR sensors allow to reduce false alarms because they rely on changes in temperature instead.

The DS-2CE11D8T-PIRL M75402 camera guarantees precise motion detector thanks to its built-in PIR sensor.

Cameras work in tandem with a Turbo HD 4.0 DVR fitted with a false alarm filter, which needs to be switched on. The alarm will be set off and footage recorded only if motion is detected simultaneously by the recorder and the PIR sensor.

An additional advantage of the camera is that you can turn on a built-in lamp to light the scene with white light, which has a dual functionality. Firstly, the intruder can be better illuminated, which translates into a higher quality video. And econdly, the light serves as an additional deterrent.

Activating a second relay in the main module of second-generation Hikvision IP intercoms.

DS-KD8003-IME1/EU (G73652) is a main door station module fitted with 2 relays, one of which can be used to control the electric door strike, while the other controls the entrance or the boom gate. By default, the second relay is switched off and invisible on indoor monitors and Hik-Connect or iVMS-4200 client apps. To activate it, go to iVMS-4200 (v.3), select Remote settings -> Intercom -> I/O module and, from the menu under "DOOR2", select "Electric Block". This will activate the second relay; it will now be displayed in the live view window of all connected monitors and client applications.

An example of a second-generation Hivision IP video intercom system being used to control the door and the entrance gate.

In the image above, the monitor (DS-KH6320-WTE1/EU (G74001)) and the main door station module (DS-KD8003-IME1/EU (G73652)) are connected to an ULTIPOWER PoE switch (N299781), which guarantees power supply and communication between the two devices. Using a router (N3255) allows access from external networks, as well as a wireless connection in the local network. The electric door strike (G74210) is released by the 12 VDC power supply unit (M1825) via one built-in relay in the door station module. The other relay controls the entrance gate.

Hikvision AXHub wireless alarm system. The AXHub Hikvision alarm system is an ideal solution for all those who wish to protect their property against unauthorized access but want to avoid ruining their home to lay the cables and mount the system...>>>more

A single-family home using the AXHub Hikvision wireless alarm system

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