RSS is a simple way for a site to share content with other sites (also called aggregated content), which is usually used for news and other orderly websites, such as blogs. The introduction of a project may include the overall introduction of news, etc. Or just extra content or a short introduction. Links to these items can usually link to all the content. Network users can read the website content that supports RSS output on the client with the help of news aggregation software that supports RSS (such as FeedDemon, SharpReader, NewzCrawler) without opening the website content page. The website provides RSS output, which is helpful for users to find the update of website content.

How does RSS work?

First of all, you usually need to download and install an RSS news reader, and then subscribe to the news columns you are interested in from the aggregated news catalogue list provided by the website. After subscribing, you will get the latest content of the subscribed news channel in time.

Features of reading RSS news?

1. There are no advertisements or pictures that affect the reading of headlines or article abstracts.

2.RSS reader will automatically update the content of your customized website to keep the news timely.

3. Users can add multiple customized RSS feeds, collect news from multiple sources and integrate them into a data stream.

With the popularity of the Internet, more and more people are used to obtaining and inquiring information through the Internet. Although various portals have sprung up like mushrooms after rain, it is really troublesome to shuttle back and forth between various websites. Search engine can help us find anything we want, but it is also more troublesome. Now there is a brand-new way of information on the Internet. He can send all kinds of information we subscribe to to our desktop, which can not only keep abreast of the latest news information, but also avoid annoying online advertisements when browsing websites. This latest information method is called information aggregation, or RSS for short.

Through RSS technology, we can receive the latest information subscribed on the computer desktop. To receive RSS information, using RSS reader is the best way. When the content of the website is updated, the RSS reader will automatically receive the latest information to the local computer desktop, and you can see the title and summary of the latest information at the same time. Click on the title to view the full text. Since the rise of Blog in China last year, the number of RSS resources has gradually increased, and major websites have also launched RSS services. Usually, as long as there is an XML logo on the website, it means that the website provides RSS services.

FeedDemon, Kantianxia Internet Information Browser, Sina Click-and-Connect Reader and Botong Zhou are common RSS readers.

= = = Basic principle of bar code reader = = =

Bar code reader is a necessary device to read the information contained in bar codes. The structure of bar code reader usually includes the following parts: light source, receiving device, photoelectric conversion part, decoding circuit and computer interface. The basic working principle is that the light emitted by the light source illuminates the bar code symbol through the optical system, and the reflected light is imaged on the photoelectric converter through the optical system to generate an electrical signal. The signal is amplified by the circuit to generate an analog voltage, which is proportional to the reflected light shining on the bar code symbol, and then filtered and shaped to form a square wave signal corresponding to the analog signal, which is interpreted by the decoder as a digital signal directly acceptable to the computer.

Ordinary bar code readers usually use the following three technologies: light pen, laser and CCD, which have their own advantages and disadvantages. It is impossible for any reader to have advantages in all aspects. The working principle, advantages and disadvantages of each reader and how to choose the appropriate barcode reader are discussed below.

= = = Working principle of light pen = = =

Light pen is the first hand-held contact bar code reader and the most economical bar code reader.

When in use, the operator needs to touch the light pen to the bar code surface and emit a small light spot through the lens of the light pen. When the light spot passes through the bar code from left to right, the light is reflected in the "empty" part and absorbed in the "bar" part, so a variable voltage is generated inside the light pen, which is used for decoding after amplification and shaping.

The advantages of light pen are: contact with bar code reading, you can clearly see which bar code is being read; The length of that read bar code can be unlimited; Compared with other readers, the cost is lower; There are no moving parts in it, which is relatively strong; Small size and light weight.

However, the use of light pens will also be subject to various restrictions. For example, it is not suitable for reading bar codes in some occasions; In addition, the light pen can only play a role when reading bar codes with specified density and good printing quality on a relatively flat surface; Moreover, the operator needs some training to use it, such as reading speed, reading angle and improper pressure, which will affect his reading performance; Finally, because it must be read by contact, when the bar code is damaged due to improper storage, or there is a protective film on it, the light pen cannot be used.

= = = Working principle of laser gun = = =

Laser gun is the most expensive of all scanners, but it can provide the longest depth of field, so it is widely used in long-distance scanning.

The basic working principle of a laser gun is that a hand-held laser reader emits a beam of light through a laser diode and shines on a rotating prism or mirror that swings back and forth. The reflected light passes through the reading window and illuminates the bar code surface. The light reflected by the rod or air returns to the reader, is collected and focused by the mirror, and is converted into an electrical signal by the photoelectric converter. The signal will be decoded by the decoding software on the scanner or terminal.

Laser readers can be used for non-contact scanning. Usually, when the reading distance exceeds 30cm, the laser reader is the only choice. Laser readers can be divided into two forms: hand-held and fixed. The laser gun is easy to use and has a wide range of bar code density. It can read irregular barcode surfaces or through glass. Because it is non-contact, it will not damage the bar code label.

But the two biggest disadvantages of laser guns are durability and price. Because the structure of laser gun adopts moving parts and mirrors, it is not as strong as CCD and light pen, because in actual use, no matter how careful the operator is when using it, the reader will inevitably fall to the ground, even if its internal components are not damaged, it is easy to reduce the performance or make the scanner completely unusable due to laser deviation; In addition, from the perspective of product cost and service life, the cost of laser gun is the highest.

= = = Working principle of CCD reader = = =

CCD is a charge-coupled device, which is more suitable for short-distance and contact reading. It is not as expensive as a laser reader, and it has no moving parts inside, so it is more durable.

The CCD reader uses one or more light-emitting diodes, and the light emitted can cover the whole bar code. The image of the bar code is transmitted to a row of photodetectors, sampled by each individual photodiode, and each bar or blank is distinguished as "black" or "white" by the detection results of adjacent detectors, thus determining the characters of the bar code. In other words, the CCD reader does not pay attention to reading every "bar" or "empty", but the whole part of the bar code.

Compared with other readers, CCD reader has many advantages: it is not as expensive as laser reader, but it also has the advantages of high bar code reading density, convenient use and less training. It is lighter than a laser reader, but stronger than a laser reader, and unlike a light pen, it can only be read by contact. The reading depth of field of a relatively new CCD has been able to meet the requirements of retail, finance and manufacturing, such as ST32 15LR of Welch Allyn, and the reading distance of low-density bar code has reached 30.48cm.

The limitation of CCD reader lies in its reading depth of field and reading width. Besides the application fields mentioned above, it is not suitable for some occasions that need long-distance reading, such as warehouses. When the bar code to be read is wide, CCD is not a good choice. Long information or low-density bar code can easily exceed the reading range of the scanning head, resulting in the bar code being unreadable.

= = = Why do you choose linear image barcode reader = = =

* * Higher use value * *

Handheld products-The IT3800 series reader produced by a Welch Alin affiliated company is a representative product of linear image readers, and all internal parts are fixed, so it is not easy to break and move, and the cost is low. With the 3-year warranty, the IT3800 series linear image barcode readers have brought longer service life, lower cost and unprecedented application value.

* * Faster output speed * *

The reading speed of IT3800 series linear image readers can reach 270 times per second, which is 6-7 times faster than ordinary laser guns!

* * Better reading ability * *

Because the laser reader uses a moving beam to scan, it will treat the stains on the label as "stripes" and the defects as "blanks". Some advanced decoding algorithms usually "filter" the correct information from the code, so these messages that are mistaken for "bars" or "empty" will slow down the decoding speed. For other readers, a big defect can even make the laser reader stop working completely, which will inevitably bring losses to those users who rely heavily on barcode data. With its advanced high-resolution optical equipment, linear image barcode reader IT3800 series can read a complete barcode image without paying attention to the defaced part, so it can read it faster and more accurately.

* * Greater flexibility * *

With the continuous expansion of bar code application field, it is necessary to use bar code reader in strong light environment. In full sunlight, it is very difficult to read with laser readers and CCD readers, or even impossible to read at all. Few readers can work in this environment, but it is 3800 series-they can scan normally in all-black to all-sunlight environment.

= = = Decoding and Interface = = =

Although each reader reads bar codes in different ways, the final result is to convert information into digital signals and then into data that can be read or compatible by computers. This is done by decoding the software in a separate device that comes with the reader or between the reader and the host. The decoder recognizes and distinguishes bar codes, and then uploads them to the host.

Uploading data needs to establish a connection or interface with the host, and each interface has two different layers: one is the physical layer (hardware) and the other is the logical layer, that is, the communication protocol. Commonly used interface methods are: keyboard port, serial port or direct connection.

When using the keyboard interface mode, the bar code symbol data transmitted by the reader is considered by the PC or terminal as the data sent by its own keyboard, and their keyboards can also play all functions.

When the keyboard connection speed is too slow, or other interface methods are not available, we will use serial port connection.

The direct connection here has two meanings, one is that the reader directly outputs data to the host without additional decoding equipment, and the other is that the decoded data is directly connected to the host without keyboard.

= = = Some common terms = = =

* * Dual interface * *: The reader can directly connect two different devices, automatically configure and communicate with each terminal. For example, a CCD is connected to IBM's POS terminal during the day, and a portable data terminal is connected at night for commodity inventory. With the built-in dual interface function, the conversion between two devices will become very easy.

* * Flash memory * *: Flash memory is a chip that can save data without power supply, and can rewrite data instantly. Welch Allyn's products mostly use flash memory to replace the original PROMs, which makes the products have stronger upgrade ability.

* * HHLC (Handheld Laser Compatibility) * *: Some terminals without decoding equipment can only communicate with external decoders. The protocol of this communication mode is usually called laser simulation, which is used to connect CCD or laser reader with external decoder.

* * RS-232 (Recommended Standard 232) * *: A TIA/EIA standard used for serial transmission between computers and peripheral devices such as bar code readers, modems and mice. RS-232 usually adopts a 25-pin plug DB-25 or a 9-pin plug DB-9, and the communication distance of RS-232 is generally within 15.24m, which is better.

* * Bar simulation * *: When the bar scans a bar code, it sends a digital image to the decoder. When the reader with decoding function is connected to an external decoder, it will adopt the wand simulation form, and the reader will translate the bar code into a digital image similar to a wand and output it to the decoder.

= = = How to choose a barcode reader = = =

The choice of bar code reader depends on the type of bar code reader and the occasion of use.

Since the birth of industry, hand-held bar code reader has been a key part in the application of automatic identification technology, and has been in a decisive position in the bar code system in industrial and application fields. Today's manufacturers have provided many cost-effective alternative products according to the various needs of consumers.

There are three main types of handheld barcode readers: contact light pen, CCD reader and laser scanner. When considering which reader can better meet your needs, it is necessary for you to know some main functional components of the handheld reader, namely 1) light source and image bar code acquisition device; 2) decoding equipment; 3) Interface mode.

The types of the three readers are determined by their reading engines. The reading engine is used to generate light and read bar codes. The reading engine of light pen uses light emitting diode (LED), CCD scanner uses electronic coupling device (CCD), and the reading engine of laser scanner uses visible light laser diode (VLD). Reading engine is the main factor affecting the cost performance of handheld readers, which determines its applicability to various purposes. After understanding their differences, you can choose a handheld reader with the best performance and value.

There are three main criteria for users to successfully select readers that meet the target requirements: working distance, label size and barcode density. The working distance refers to the distance between the scanner and the label when reading. The scanning distance can range from zero (contact) to several feet, and the reading distance is determined by the bar code reader. The label size refers to the entire width of the bar code to be read; Bar code density refers to the width of the smallest bar or empty module that can be read. These three factors are interrelated, for example, the size of the label and the bar code with large empty modules can also support a large reading distance. Light pen, CCD reader and laser scanner have different performances, and their prices and service life are also different. In every aspect, users should make different considerations.

* Working distance (depth of field)

The depth of field of the scanner must be clearly defined. Does the operator touch the label surface or keep a certain distance during operation? Generally speaking, contact reading is used in retail, office and factory applications, while remote reading is usually used in warehouse, distribution and transportation applications.

The depth of field of three types of readers is very different. As can be seen from their names, the contact light pen needs to be in contact with the label surface. The working distance of CCD readers is limited to one or two feet, but the latest readers have effectively extended the depth of field to 7 inches (17.8 cm); ). The laser scanner has the largest depth of field, ranging from 8 inches to 30 inches (20.32-76.2 cm). Some special laser guns specially designed for reading large bar codes have a range of several feet.

The difference in depth of field can be reflected by the price of the reader. Light pen is usually the most economical reader, laser gun is the most expensive, and CCD reader is in between. Because these readers are all designed with solid crystals, they have excellent life cycle cost.

* Label size/label density

Label density refers to the minimum width of a bar or an empty cell, in thousandths of an inch, that is, "mill". For linear and one-dimensional bar codes, the size of the label is considered as the width of the label. High-density bar codes (below 7 mils) need to be read at a short distance, and low-density bar codes (above 15 mils) can be read at a long distance.

When choosing a CCD reader, be sure to know the entire width of the scanned barcode. In most cases, the maximum width of the barcode that a CCD reader can read is limited by the opening width of the reader, and some special readers for reading large barcodes need special design. Because the light generated by light pen and laser gun can move on the surface of bar code, both readers can read wider bar codes.

If you decide to choose a light pen, you must consider the aperture of the light pen in terms of hardware. The width of the hole should be approximately equal to the width of the narrowest bar or space of the X-dimensional bar code to be read. If the aperture is too large, adjacent bar codes will appear in the scanning window when reading, which will increase the reading difficulty; If the aperture is too small, the scanner will mistake some printing defects on the bar code for bars or blanks that should not exist in the bar code, resulting in reading errors.

* image decoding

Once the scanner's beam and recognition system capture the bar code or empty cells, the information must be converted into symbols that can be recognized by the host system. This process is called decoding. The decoding function module can automatically identify the scanned barcode type and load the corresponding decoding algorithm to realize the decoding of the barcode on the label.

The decoded information is formatted as standard RS-232 serial port data, or converted into keyboard commands and transmitted to the host computer system. The decoded information is transmitted to the RS-232 communication interface through the cable, and the keyboard data is transmitted to the keyboard port of the terminal through the Y-shaped cable.

"Interface" is used to indicate the connection technology between barcode reader and host or terminal. The serial port inserts the scanned data into the RS-232 signal between the host or terminal, while the keyboard port regards the data as a series of keyboard signals. Through the programmed software, the bar code reader can scan the bar code menu to select the parameters of the terminal and interface.

A few years ago, the decoding and communication functions of readers needed to be completed by independent devices. The bar code reader outputs laser calibration signal (HHLC) or light pen analog signal to the external decoding box, and the decoding box completes the decoding and transmission functions. At present, the reader manufacturers have integrated the decoding components of three types of barcode readers into one component, that is, the decoded output scanner (DOS). The decoded output scanner uses plug-ins, which provide exactly the same performance as the code box and are cheaper.

When two or more different types of scanning devices work in their respective decoding states at the same time or need an auxiliary port (for integrating measurement, printing or other I/O devices), additional decoding ports are still needed. However, from the convenience of integration and low system cost, this integrated decoding reader is still an excellent choice.

* Interface equipment

After decoding, the data on the tag must be transmitted to the host computer system. The functions of serial port and keyboard port used to format data and output have been explained in the previous section. Of course, the reader must be physically connected to the host system, so consumers need to identify the type of physical interface of the PC or system. Manufacturers' handheld readers support hundreds of terminal types and provide hundreds of interface lines, so users can order the appropriate interface lines according to their own needs.

Because the decoding output reader can support multiple terminal interfaces with one component, some manufacturers of CCD and laser handheld readers have standardized the universal interface line scheme, so that users do not need to reserve a large number of interface lines, and can support CCD scanners and laser readers at the same time with the universal interface line, saving time and money.

Light pen, CCD reader and laser scanner all have good cost performance in application. After understanding some main functions and price differences, I hope you can choose the most suitable handheld barcode reader.