TV-SAT, CCTV, WLAN Dipol Weekly Review

Underground WiFi.

Korean researchers at the Electronics and Telecommunications Research Institute (ETRI) have developed a wireless underground communication system that operates at distances of up to 100 metres. Unlike traditional radio wave-based technologies, it uses magnetic induction, thus avoiding the problems associated with signal penetration through the ground. This opens up a new channel of communication that can help, among other things, in checking whether people trapped underground are alive after the collapse of mines or other structures, as well as in rescue operations and military operations.

In mines, the radio signal fades very quickly, so traditional wireless systems there do not work. The researchers therefore focused on using a stable magnetic field and created a low-frequency communication system. The research used a 0.9-metre diameter transmitting antenna, a small magnetic field receiving sensor, a frequency of about 15 kHz and a data rate of 2-4 kbps, which is sufficient for voice transmission. QPSK (quadrature phase modulation) modulation was used for transmission. Tests were carried out in a limestone rock environment, which is particularly effective at blocking traditional radio signals.

It was possible to carry out two-way communication over a distance of 100 metres in a straight line - from the mine entrance to the fifth level underground. This is the first such result in the world, far exceeding previous achievements, which were limited to a few tens of metres. The institute stresses that it is working on solutions to enable this technology to work with personal devices such as smartphones. In the future, this could allow the creation of wireless access points connecting the surface to the underground.

This is not the first time magnetic induction has been used to transmit signals. The very concept of this technology emerged in 2023, when researchers proved the possibility of ground-penetrating communication using a voltage-controlled method. At that time, a range of around 40 metres was achieved. So we can see significant and rapid progress in the work concerning this field of communication.

COMBO type antennas for digital terrestrial TV DVB-T2.

DVB-T2 television antennas of the COMBO type with H/V polarisation are used to receive signals in the VHF and UHF bands, allowing reception of all DVB-T2 terrestrial TV multiplexes. The selection of a suitable DVB-T2 TV antenna depends on many factors, so there is no single universal solution for all users. Of key importance is first of all the distance from the transmitter and the signal strength in a given location. In locations close to the transmitter (up to 40 km for a strong DVB-T2 transmitter), where the signal is strong and stable, passive antennas such as the DVB-T2 TV Antenna Y3 PASSIVE COMBO A2120, which do not require power and are less prone to overdrive, work well.

Another important factor is the terrain and surroundings - buildings, trees or other obstacles that may weaken the signal or cause its reflections. In such conditions, active antennas with an amplifier may be a better choice, such as the DVB-T2 DIPOL SMART CITY COMBO A2050 TV antenna, which improve reception quality in more difficult conditions, especially in cities.

The possibility of supplying power to the antenna and the length of the antenna cable are also important - the longer the cable, the greater the signal loss. In such cases, it is worth considering an intermediate solution, i.e. an antenna with the possibility of operating in both passive and active mode (COMBO 0-24 V), which allows the mode of operation to be adjusted to the current installation conditions.

The DVB-T2 DIPOL SMART HORIZON COMBO TV antenna with H/V polarisation (DC 0-24 V) A2270 is a larger design, which translates into its higher energy gain and better directional properties. For this reason, it is primarily designed for installation in locations away from the transmitter where the signal is weaker and requires more effective reception. The ability to operate in both passive and active mode (when powered) further enhances its versatility.

Name	Y3 PASSIVE COMBO	SMART CITY COMBO	SMART HORIZON COMBO
Code	A2120	A2050	A2270
Band	VHF + UHF
Operating mode	passive	passive/active (DC 5... 24 V)
Gain
Distance from transmitter	up to 40 km	up to 40 km	up to 80 km
Dimensions [mm]	950x530x740 (pol. V), 950x740x420 (pol. H)	1108x503x740 (pol. V), 1156x740x403 (pol. H)	1156x502x740 (pol. V), 1156x740x605 (pol. H)

Simple surveillance system with face recognition.

Hikvision IP DVRs of the NXI-K and NXI-I series feature face capture and analysis on a specified number of channels. It is possible to create libraries of faces that will later be used to search the recordings. It is also possible to specify the associated actions that will be carried out in the event of a correct or incorrect comparison between a detected face and a face that is in the library, e.g. triggering a beep in the recorder, an alarm in the monitoring centre, sending an e-mail, controlling an alarm output, etc. Faces already recorded on the DVR or from an external source can be added to the library. Recordings stored on the DVR can be easily and quickly searched by pointing to a specific face, on channels where the face recording and comparison function was active.

The diagram below shows a monitoring system based on the DS-7608NXI-K2 K22076 DVR. Connected to the DVR are 7 cameras DS-2CD2046G2H-IU K03218 which are used from general monitoring. One channel has been connected to the DS-2CD2646G2HT-IZS K05314 camera with a resolution of 4 Mpix, which, combined with the functionality of the DVR, is used for face analysis and search. Remote access to the system from the external network is performed using the Mercusys MW305R N2931 router.

Fiber optic categories and designations.

When studying fiber optic network design documentation, one will come across many designations for fiber optic cables and fibers. There are several popular styles of fiber naming. Some of them come directly from the designations proposed by standards and recommendations. Others are a confusion of these designations with abbreviated descriptions on the outer sheaths of cables.

The best-known way of describing fibers comes from a series of recommendations of the ITU-T organization. This naming and categorization method (G.65xx) can be found most often in catalog data offered by fiber optic cable manufacturers and vendors. On the other hand, designers of telecommunications networks, when describing cabling issues in detail, can use a European standard issued by the IEC to describe fibers: EN 60793-2-50. According to it, single-mode fibers are category B, while multimode fibers are category A1. Each category, of course, also has subcategories, the equivalents of which can be found in the IUT-T recommendations.

The third and final way is through designations introduced by the company standards of large telecommunications operators. Within their own networks, they may use alternative designations to those proposed by the standards. An example is Orange, which has introduced the "J" category for single-mode fibers, along with the corresponding subcategories.

For multimode fibers, ITU-T has issued one recommendation: G.651.1 while not proposing a subcategory of these fibers (the recommendation refers to other documents in this regard). The most popular classification of multimode fibers is introduced by the structured cabling standard ISO/IEC 11801. Designations: OM1, OM2, OM3, OM4 and OM5 are described in this very document. A much less popularized (but still found) way of marking multimode fibers is included in EN 60793-2-10. These are respectively: A1b for OM1 fibers, A1a1 for OM2 fibers, A1a2 for OM3 fibers and A1a3 for OM4 fibers.

What cameras are compatible with the AcuSeek feature?

AcuSeek is an advanced feature available on Hikvision's latest IP DVRs that introduces a completely new way of searching through video recordings. It uses multimodal artificial intelligence capable of simultaneously analysing camera images and natural user text queries. As a result, the system is able to understand the content of the footage and the intentions of the person using the search engine, making it possible to find a specific video moment in seconds, without having to manually review the footage. Guanlan's AI-based technology enables it to analyse objects, people, vehicles, colours and behaviours, as well as interpreting commands typed in colloquial language, such as 'person in glasses with red handbag'. The system combines this information in a single working environment, matching the correct parts of the recording with high precision.

AcuSeek is particularly well suited to locations where it is crucial to find unusual events quickly by searching through footage from multiple cameras simultaneously. It is ideal for facilities such as logistics centres, retail outlets, public buildings, car parks, administrative institutions or offices. The function also remains effective in the case of unusual events, allowing specific situations recorded on footage to be found with a high degree of precision.

HIKVISION 2 line mode: smart events	2xx3G2	V5.7.17SP
	2x83G2(T)	V5.7.4_240319
	2xx6G2/G2H	V5.7.17SP
	2xx7G2	V5.7.17SP
	2xx7G2H	V5.7.17SP
	2xx7G3	V5.8.10

Basics of IP addressing - part 3: network and host address.

In the previous Newsletter, the subnet mask was discussed. More often than not, the third will detail how to calculate the network address and host (IPv4) based on the netmask. The function of the mask is to determine how many consecutive bits in the IP address constitute the network address. The remaining bits already determine the address of a specific host on that network (the address of the end device). Where the bit in the mask is set to 1, the corresponding IP address bit belongs to the network address, while where the bit is 0, the corresponding IP address bit belongs to the host address.

The subnet mask bits are always set to 1, starting with the most significant bit (commonly the oldest), for example:

As seen in this case, the network address is:

While calculating a network address, and when the device IP address and mask, are available, the AND function should be applied (the result contains one when there is one in both strings):

The result of the AND function is the network address which, after conversion to decimal, has the form: 192.168.11.128.

Knowing the subnet address, the broadcast address can be easily calculated. To this end, the mask bit negation is used, and the resulting number is added to the network address:

Every octet has to be added to its corresponding octet of the network address. Since the first 3 octets are 0, just the last one is added: 128+127=255. The broadcast address sought in this network is therefore: 192.168.11.255.

The ability to calculate addresses is useful, for example, when the provider assigns a pool of IP addresses to the user. The provider rarely provides a list with the specified host, network or broadcast addresses. Only the network address and mask is specified in the provider documentation. For example, a user is notified of being given the 62.121.130.32/29 addressing (the /29 means the mask 255.255.255.248). The user has to calculate that the network address is 62.121.130.32, the host addresses are from 62.121.130.33 to 62.121.130.38 and the broadcast address is 62.121.130.39.

Optical-copper RTV/SAT installation using the SIGNAL PROfessional line of devices. This solution can be used in large facilities where the distance between cages is more than a few dozen metres. The fibre optic cable provides excellent insulation against surges. This means that any surges induced in the vicinity of the antennas will stop at the optical transmitter installed immediately behind them - all other components of the installation are 100% protected. Signal PROfessional uses 1 optical fibre to transmit the entire bundle of TV signals...>>>more