Coşul este gol



DIPOL Weekly Review - TV and SAT TV, CCTV, WLAN
No. 38/2007 (Nov 5, 2007)
What about Polish DVB-T? In Poland there is planned DVB-T system using MPEG-4 compression. The accepted in September "Program of introducing terrestrial broadcasting of digital TV (DVB-T)" deals only with video standard. There is no decision made whether the sound will be coded as ACC, or Dolby Digital + files.
In this situation there are two possible solutions: each existing TV station will create its own independent multiplex, or all television channels will be put into one common multiplex. In the first case the digital receivers should be equipped with both codecs, in the second case - there is a chance that the broadcasters will agree on one standard. In either case producers of the equipment will need about 6 months' time to prepare the receivers.
Taking into consideration snail's pace of decision making, we are almost 100 % sure that the Olympic Games in Beijing will not be transmitted in DVB-T system.
How to do satellite installation: with QUAD, or QUATRO and multiswitch? To make the decision we have to know functional requirements. For connecting only four receivers with single tuners or two with double tuners (PVR), QUAD converter will do. But we have to remember that this choice blocks development of the installation in the future (adding next outlets). Expansion of the installation by adding second satellite may also be troublesome, due to requirements of high separation between inputs of the switch (minimum 25 dB) and use of converters with low crosstalk. A proven and tested solution is the set of A9831 and R852506 (4 pcs.).
So in many respects multiswitch installations are the better choice, allowing to build installations from 4 to 200 outlets, ensuring reception of two satellites - e.g. based on the multiswitches MS-952/951.
CE-marked broadband antenna preamplifiers. The antennas with built-in board amplifiers were taken of the shelves several years ago, due to lack of compliance with CE requirements. But now, using the LNA-101 B4007 and LNA-169 B4008 preamplifiers, antenna manufacturers may equip their products with the new generation of RF amplifiers suitable for putting in antenna box. Such preamplifier is an ideal solution in the case of low-level signals, with low S/N ratio. The amplifiers cover BIII, BIV, and BV bands. Their housings ensure high screening efficiency.
Shielded Antenna Preamplifier LNA-101 15dB
Shielded Antenna Preamplifier LNA-169 24dB
LNA-101 15 dB B4007
LNA-101 24dB B4008
Multiswitch installation in Warsaw. Leg-Bud, a real estate developing company building gated condominiums in Warsaw and its surroundings, decided to provide new apartments with satellite TV by implementing multiswitch installation. The system done by Lima company ensures reception of terrestrial and satellite broadcasts (from one satellite position, but it provides access to all Polish digital platforms) in 3 buildings (each having 50-80 apartments) in Legionowo near Warsaw. The installation has been designed on the basis of multiswitches from Terra MSR family and satellite splitters and taps of SS series. The terrestrial signals has been prepared for distribution by the RF amplifier WWK-861 R89860.
Due to extensive network (100m long vertical ducts), there has been used high-quality coaxial cable - TRISET-113 E1015_500.
There have been achieved very good results - even with the weakest transponders (e.g. 10719 MHz) the C/N parameter exceeds 11 dB, which guarantees quality reception at each outlet.
Connection box in one of the buildings
Military exercises on computer's screen. Video monitoring systems find new applications. Recently at Chinese training ground there was used IP CCTV technology to enable the command to watch the results being obtained by the soldiers. The system was based on analog CCTV cameras and video servers ACTi ACD-2100 K2113. The MPEG-4 stream was transmitted wirelessly to a server managed by ACTi software package NVR K3032. Use of wireless transmission allowed quick deployment of the system in the area where any cable solution was impossible. Furthermore, after the maneuvers had been completed, the system could be transferred to another location
Pictures taken during the maneuvers in China. In the right bottom picture there are visible cameras directed towards shooting targets.
Monitoring of schools - tapping not allowed. Gazeta Prawna (translation: Law Newspaper) has published the interpretation of Polish ombudsman Mr. Jan Kochanowski on sound recording issue in monitoring systems installed in schools.
"Installation of microphones in schools, which enables the operator to record private conversation of students and teachers, may violate the constitutional right to privacy.
...This requirement significantly raises the cost of monitoring system, because the directive says that sound should be recorded in the band up to 6 kHz. It is possible in the case of 10 % of the devices used for monitoring of mass events available in the market. The rest of the equipment, the much cheaper alternative, is capable of recording sounds up to 3.5 kHz.
According to our knowledge local governments order the cheaper DVRs, hoping that no one will verify the parameters that are unimportant for practical applications.
- If education department resigned from the requirement of recording sounds up to 6 kHz, the monitoring systems could be cheaper even by 20 % - it is the conclusion of Tadeusz Szydlowski. Thanks to the step, only this year additional 600 schools could be subsidized, or those which got public funding - would have ca. 440 Euro extra. Simply the local governments could purchase more cameras. The current regulations do not allow to spend public money efficiently." ... more (in Polish only)

For video monitoring of schools, DIPOL offers 8-channel DVR M85075, 16-channel DVR CPD-507/787 M8534, or its version with DVD recorder - CPD-507 M8537. Our Technical Department recommends to employ 16-channel DVR, even if the number of cameras is currently lower.
Video surveillance in schools - the article analyzing specific features of school monitoring systems.
Free software package P6032 for CCTV monitoring and recording video and sound from PiXORD devices. Every IP CCTV device from PiXORD is supplied with professional software package P6032 for managing CCTV system.
Main features of the software:

  • live monitoring and recording images from 32 cameras (continuous or motion-triggered)
  • PTZ control
  • advanced functions of viewing archives and exporting them to any video format used by O.S.
  • export of video to any external monitoring center - remote monitoring
  • typically a system equipped with 500 GB HDD is capable of recording Full D1 images at 25 fps (motion detection) for a week's time (16 cameras).
The software can be only used with PiXORD equipment.

Screenshot from PiXORD P6032 utility
Motion detection - efficient use of disc space in DVRs. Use of motion detection enables the administrator to save the installed space disc in the DVR. Recording of images from cameras is performed only for a certain period of time after some motion has been detected. With static images the action is suspended. This solution allows to gather only alarm events. Of course, there are possible false alarms, but it is rather an exception - caused by improperly defined area or sensitivity of motion detection.
An interesting feature of CPD recorders is possibility of defining periods of recording - in time schedule recording mode and in motion detection mode, e.g. during working hours (say 7:45 to 16:15) - continuous recording, and for the rest of the time (when the place should be empty) - motion detection.
CPD recorders
How to increase system throughput - packet aggregation in Raptor devices. Because the 802.11 standard protocol does not guarantee efficient work with a large number of packets, THEMAX company has developed it own transmission protocol TFPP (Themax Fast Pooling Protocol). Aggregation of packets allows to increase channel throughput even up to 5 MBps, and to transfer up to 30,000 packets per second. Raptor devices support extended protocol functions such as advanced pooling with priority setting for the stations requiring broader band. To get the advantage of the new TFPP protocol, the user has to install the newest firmware (v2.0r10) and switch on the option in all Access Points and Clients.
Outdoor Wi-Fi AP/APC: RAPTOR RPT-23XR (5GHz, 802.11a)Outdoor Wi-Fi AP/APC: RAPTOR RPT-23XR (5GHz, 802.11a)MPEG-4 IP Camera: ACTI CAM-5321 (Day/Night)IP Speed Dome Day/Night Camera: ACTi CAM-6621 (MPEG-4)
Diagram showing application of Raptor devices in city monitoring system. Due to the special features described above, the system is capable of smooth transmission of video streams from IP cameras to remote monitoring center.
George Popescu
Consiliere clienţi
Dacă doriţi să primiţi Săptămânalul Dipol prin email, introduceţi adresa:
Nou în bibliotecă
Regulamentul | Garanție | Reclamaţii | Download
| Cookies | Politica de confidentialitate Toate drepturile rezervate © 1996-2024 DIPOL sp.j.