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

Will CAPTCHA soon be history?

Anyone who surfs the Internet on a daily basis has certainly come across the CAPTCHA security system, with which the users must prove to the visited websites that they are not robots. For Internet users, this solution is often annoying, but so far it has been protecting websites against spam and other threats. But will not "artificial intelligence" overcome it?

An example of CAPTCHA

CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) is a type of technique used as a security feature on websites, whose aim is to allow only human-filled data to be sent. This technique protects, among other things, forms against spam, portals against creating accounts by machines, discussion forums and blogs - from advertisements in comments, etc. The system verifies and recognizes human beings by assigning them tasks and expecting proper solutions. The most commonly used security tasks require recognition of short strings of characters provided in the form of images (usually randomly selected characters or short words). Such images are readable for humans, but very difficult to be recognized by software means. There are many other CAPTCHA implementations and variations, including sound solutions (the system reads the task) and mixed forms, e.g. graphic and text combinations.
Such protection has both supporters and opponents. A typical technical error of CAPTCHA and something that can be very annoying is the construction of images that they are difficult or even impossible to read even by people. In the case of text tasks they sometimes have a level of difficulty that enforces the use of an encyclopedia.

The assumption that computers are not able to read CAPTCHA, which has been so far taken for granted, turns out to be illusory. Researchers at Lancaster University in Great Britain and Northwest University and Peking University in China have developed a program that is able to break such protections. The developed algorithm operates on the basis of the "Generative Adversarial Network" technique, which uses two neural networks and is able to break the protections in just 0.05 seconds. The system's learning process consists in providing a certain number of samples. In the experiment, 500 images were the sufficient set, and the rest was learned by the system thanks to CAPTCHA's automatic generation of patterns. The breaking of the protection was tested on 33 schemes, 11 of which were those used by eBay, Wikipedia, and Microsoft. The creators of the algorithm believe that this is the first signal that CAPTCHA, at least in the form we know of, goes into history.

Measurements of digital DVB-T/T2 signals - MER parameter.

The majority of commercially available meters of digital television signals allows only signal level measurements expressed in dBμV and an approximate estimate of their quality (usually as a percentage). Usually, it does not allow for precise positioning of the antenna. An important parameter that should be taken into account when measuring DVB-T signals is MER. MER (Modulation Error Ratio) can be treated as a measure of the distance of the received signal to the digital cliff. Without knowing this parameter, the antenna installer cannot guarantee stable reception in adverse weather conditions or other situations when the signal can fluctuate (e.g. interfered by a passing truck).

The appropriate safety margin (sufficiently large distance from the "digital cliff") confirmed by MER measurement allows the installer to avoid this type of situations. The recommended and minimum values of MER required for proper reception depend on the modulation technique. In the case of 64-QAM modulation, they are 31 dB and 26 dB respectively.

The Signal WS-6975 R10514 meter can measure MER parameter of DVB-T/DVB-T2 signals.
The built-in receiver and LCD screen provide the live preview of the tested channel.

We sell a new DVB-T/T2 meter with MER measurements, Signal WS-6975 R10514, suitable also for measuring parameters of signals from HD multiplexes. Thanks to the built-in receiver, the user can monitor the currently tested channel. The measured parameters include signal level expressed in dBμV, C/N ratio, BER (Bit Error Rate) and MER, which allows for precise positioning of terrestrial antennas, tuning of filters, adjustment of amplifiers, maintenance and troubleshooting antenna systems.

Selecting shelves for RACK cabinets.

Shelves in RACK cabinets can be used for placing various devices that do not comply with RACK 19" standard, such as UPS units. The important dimension of a shelf is its depth, allowing for mounting the shelf to the front and rear rails of the RACK cabinet.

It is worth remembering that four-point mounted shelves are not components of the RACK standard, and as proprietary solutions are suitable only for the cabinets of a particular manufacturer. For example, the "Shelf for SIGNAL 19" standing RACK cabinet (600mm)" offered by DIPOL is suitable for Signal RACK cabinets with 600 mm depth (so the 600 mm is not the depth of the shelf). Four-point mounted shelves are indispensable in the case of heavy devices, as they can carry much heavier equipment than the only front-mounted versions.

The shelves with lists of compatible RACK cabinets:

How to upload screenshots from cameras on a cloud server?

Hikvision monitoring devices have the ability to send screenshots from cameras to cloud servers. They are transmitted in the form of 3 photos captured from the auxiliary stream at the time of the detection of an event. The supported events:

The screenshots can be uploaded to popular cloud storage services:

Configuration of recording images from Hikvision NVR on GoogleDrive

The snapshots can be used as a backup of the most important information that can be remotely viewed at any moment.

Hikvision IP cameras in black housings.

In some cases, designers or investors require to install cameras in dark housings. DIPOL offers Hikvision IP cameras in black housings, belonging to the EasyIP 3.0 series characterized by a high quality imaging and extreme sensitivity provided by Dark Fighter technology. The series also implements VCA functions: detection of faces, virtual line crossing, intrusion detection, detection of leaving/taking objects. These features make the cameras perfect devices for implementing advanced video surveillance projects.

Why is the calibration of fiber optic splicers important?

The calibration of a fiber optic fusion splicer consists in adjusting the power and temperature of the electric arc to the current environmental conditions. Properly adjusted arc parameters guarantee high quality of the splices, both in terms of optical attenuation and mechanical strength. Therefore, the calibration should always be performed before splicing operations - at the beginning of work or in the case of changing the environment (e.g. from indoor to outdoor part of a system, especially when the difference in temperature between the locations is high).

The most expensive models of fusion splicers are equipped with pressure and temperature sensors that allow for automatic calibration in real time. Most popular devices require manual calibration taking several minutes. Omission of calibration will not always mean bad splices. However, there is a risk that some of them, even those indicating low attenuation, will be very weak and unstable mechanically (e.g. in the case of too low splicing temperature they can sometimes crack after an hour).

Signal Fire AI-8 L5870 fusion splicer uses popular calibration method - the fibers located in the splicing chamber are subjected to a number of electric arcs. The fibers are melted and the software of the splicer measures and analyzes the distance at which the fiber faces move backward. On the basis of the measurements, the splicer determines the appropriate parameters of the electric arc.

The calibration of Signal Fire is done by selecting "Arc Calibration" option in the management application. When the fibers are inserted into the splicing chamber and the cover is closed, the calibration process starts automatically. When finished, the splicer switches to normal mode, i.e. is prepared for regular splicing operations.

In the winter period, installers should pay particular attention to the proper preparation of the splicing equipment before commencing work. A splicer that has spent the night in a car parked outside and brought to a room with room temperature, is not suitable for immediate operation: the fogged camera lens may result in erroneous fiber positioning and auto-focus problems. To avoid such problems, installers should store and transport the precise devices in proper conditions.

Signal Fire AI-8 L5870 fusion splicer

The role of PIR detectors in CCTV cameras. The HD-TVI DS-2CE11D8T-PIRL M75402 camera has been equipped with PIR sensor. The purpose of the PIR sensor is a better detection and recognition of motion detection. Video motion detection relies on image analysis and can result in multiple false alarms. A typical example is the detection of branches swaying in the wind or falling rain. A lot of alarms are also generated by the lack of proper lighting. Each unimportant alarm translates into loss of disk space and the need to browse unnecessary recordings. The PIR detector significantly limits occurrence of such alarms, because it works based on the detection of temperature changes... >>>more

With the built-in PIR sensor, the DS-2CE11D8T-PIRL M75402 camera ensures very reliable motion detection