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soukacatv · 6 years ago

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Reading About the Analog vs. Digital Signals | Soukacatv.com

Overview

We live in an analog world. There are an infinite amount of colors to paint an object (even if the difference is indiscernible to our eye), there are an infinite number of tones we can hear, and there are an infinite number of smells we can smell. The common theme among all of these analog signals is their infinite possibilities.

Digital signals and objects deal in the realm of the discrete or finite, meaning there is a limited set of values they can be. That could mean just two total possible values, 255, 4,294,967,296, or anything as long as it’s not ∞ (infinity).

Working with electronics means dealing with both analog and digital signals, inputs and outputs. Our electronics projects have to interact with the real, analog world in some way, but most of our microprocessors, computers, and logic units are purely digital components. These two types of signals are like different electronic languages; some electronics components are bi-lingual, others can only understand and speak one of the two.

In this tutorial, we’ll cover the basics of both digital and analog signals, including examples of each. We’ll also talk about analog and digital circuits, and components.

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Suggested Reading

The concepts of analog and digital stand on their own, and don’t require a lot of previous electronics knowledge. That said, if you haven’t already, you should peek through some of these tutorials:

Voltage, Current, Resistance and Ohm’s Law

What is a Circuit

And some mathematics concepts: reading graphs, and understanding the difference between finite and infinite sets.

Analog Signals

Define: Signals

Before going too much further, we should talk a bit about what a signal actually is, electronic signals specifically (as opposed to traffic signals, albums by the ultimate power-trio, or a general means for communication). The signals we’re talking about are time-varying “quantities” which convey some sort of information. In electrical engineering the quantity that’s time-varying is usually voltage (if not that, then usually current). So when we talk about signals, just think of them as a voltage that’s changing over time.

Signals are passed between devices in order to send and receive information, which might be video, audio, or some sort of encoded data. Usually the signals are transmitted through wires, but they could also pass through the air via radio frequency (RF) waves. Audio signals, for example might be transferred between your computer’s audio card and speakers, while data signals might be passed through the air between a tablet and a WiFi router.

Analog Signal Graphs

Because a signal varies over time, it’s helpful to plot it on a graph where time is plotted on the horizontal, x-axis, and voltage on the vertical, y-axis. Looking at a graph of a signal is usually the easiest way to identify if it’s analog or digital; a time-versus-voltage graph of an analog signal should be smooth and continuous.

While these signals may be limited to a range of maximum and minimum values, there are still an infinite number of possible values within that range. For example, the analog voltage coming out of your wall socket might be clamped between -120V and +120V, but, as you increase the resolution more and more, you discover an infinite number of values that the signal can actually be (like 64.4V, 64.42V, 64.424V, and infinite, increasingly precise values).

Example Analog Signals

Video and audio transmissions are often transferred or recorded using analog signals. The composite video coming out of an old RCA jack, for example, is a coded analog signal usually ranging between 0 and 1.073V. Tiny changes in the signal have a huge effect on the color or location of the video.

An analog signal representing one line of composite video data.

Pure audio signals are also analog. The signal that comes out of a microphone is full of analog frequencies and harmonics, which combine to make beautiful music.

Digital Signals

Digital signals must have a finite set of possible values. The number of values in the set can be anywhere between two and a-very-large-number-that’s-not-infinity. Most commonly digital signals will be one of two values – like either 0V or 5V. Timing graphs of these signals look like square waves.

Or a digital signal might be a discrete representation of an analog waveform. Viewed from afar, the wave function below may seem smooth and analog, but when you look closely there are tiny discrete steps as the signal tries to approximate values:

That’s the big difference between analog and digital waves. Analog waves are smooth and continuous, digital waves are stepping, square, and discrete.

Example Digital Signals

Not all audio and video signals are analog. Standardized signals like HDMI for video (and audio) and MIDI, I2S, or AC'97for audio are all digitally transmitted.

Most communication between integrated circuits is digital. Interfaces like serial, I2C, and SPI all transmit data via a coded sequence of square waves.

Serial peripheral interface (SPI) uses many digital signals to transmit data between devices.

Analog and Digital Circuits

Analog Electronics

Most of the fundamental electronic components – resistors, capacitors, inductors, diodes, transistors, and operational amplifiers – are all inherently analog. Circuits built with a combination of solely these components are usually analog.

Analog circuits are usually complex combinations of op amps, resistors, caps, and other foundational electronic components. This is an example of a class B analog audio amplifier.

Analog circuits can be very elegant designs with many components, or they can be very simple, like two resistors combining to make a voltage divider. In general, though, analog circuits are much more difficult to design than those which accomplish the same task digitally. It takes a special kind of analog circuit wizard to design an analog radio receiver, or an analog battery charger; digital components exist to make those designs much simpler.

Analog circuits are usually much more susceptible to noise (small, undesired variations in voltage). Small changes in the voltage level of an analog signal may produce significant errors when being processed.

Digital Electronics

Digital circuits operate using digital, discrete signals. These circuits are usually made of a combination of transistors and logic gates and, at higher levels, microcontrollers or other computing chips. Most processors, whether they’re big beefy processors in your computer, or tiny little microcontrollers, operate in the digital realm.

Digital circuits make use of components like logic gates, or more complicated digital ICs (usually represented by rectangles with labeled pins extending from them).

Digital circuits usually use a binary scheme for digital signaling. These systems assign two different voltages as two different logic levels – a high voltage (usually 5V, 3.3V, or 1.8V) represents one value and a low voltage (usually 0V) represents the other.

Although digital circuits are generally easier to design, they do tend to be a bit more expensive than an equally tasked analog circuit.

Analog and Digital Combined

It’s not rare to see a mixture of analog and digital components in a circuit. Although microcontrollers are usually digital beasts, they often have internal circuitry which enables them to interface with analog circuitry (analog-to-digital converters, pulse-width modulation, and digital-to-analog converters. An analog-to-digital converter (ADC) allows a microcontroller to connect to an analog sensor (like photocells or temperature sensors), to read in an analog voltage. The less common digital-to-analog converter allows a microcontroller to produce analog voltages, which is handy when it needs to make sound.

Resources and Going Further

Now that you know the difference between analog and digital signals, we’d suggest checking out the Analog to Digital Conversion tutorial. Working with microcontrollers, or really any logic-based electronics, means working in the digital realm most of the time. If you want to sense light, temperature, or interface a microcontroller with a variety of other analog sensors, you’ll need to know how to convert the analog voltage they produce into a digital value.

Also, consider reading our Pulse Width Modulation (PWM) tutorial. PWM is a trick microcontrollers can use to make a digital signal appear to be analog.

Here are some other subjects which deal heavily with digital interfaces:

Binary

Logic Levels

Serial Communication

SPI Communication

I2C Communication

IR Communication

Or, if you’d like to delve further into the analog realm, consider checking out these tutorials:

Voltage Dividers

Resistors

Diodes

Capacitors

Transistors

Established in 2000, the Soukacatv.com (DSW) main products are modulators both in

digital and analog modulators, amplifier and combiner. We are the leading communication supplier in manufacturing the headend system in China. Our 16 in 1 and 24 in 1 now are the most popular products all over the world. For more, please access to https://www.soukacatv.com/.

Source: https://learn.sparkfun.com/tutorials/analog-vs-digital/all

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soukacatv · 6 years ago

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What is Modulation? Why Do We Need it? | Soukacatv.com

What is Modulation?

Transmission of information by communication systems over large distances is quite a feat of human ingenuity. We can talk, video chat and text anyone on this planet! Communication system uses a very clever technique called Modulation to increase the reach of the signals. Two signals are involved in this process.

Message signals also known as baseband signals are the band of frequencies representing the original signal. This is the signal to be transmitted to the receiver. Frequency of such a signal is usually low. The other signal involved with this is a high frequency sinusoidal wave. This signal is called the carrier signal. The frequency of carrier signals is almost always higher than that of the baseband signal. The amplitude of the baseband signal is transferred to the high frequency carrier. Such a higher frequency carrier is able to travel much farther than the baseband signal.

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But that’s not the only advantage of modulation. What is the need for modulation?

Size of the Antennae

When the transmission occurs over free space, the antennae radiate the signal out and receiver receives it. In order to operate efficiently, antennae need to be in order of the magnitude of wavelength of the transmitted signal.

L=λ=uϑ=(3∗108)ϑHz

Speech frequencies range from 20 Hz to 20 kHz. Suppose this is a frequency of 20 kHz and it is radiated out to a receiver through a channel of free space.

Length of Antennae=3∗10820∗103=15000m=15km

It is impossible to build an antennae this big. Instead say we give modulation a chance and use a 1000 kHz carrier wave to carry the signal. Length of the antennae now would be;

Length of Antennae=3∗1081000∗103=300m

This is much more doable and this example clearly shows us how hugely the process of modulation is enabling communication systems.

Wireless Communication

By using modulation to transmit the signals through space to long distances, we have removed the need for wires in communication systems. The technique of modulation helped humans to become wireless. Telephones no longer had to be plugged to a wall. Using a mobile phone went from a dream to the next big thing.

Interference from other signals

This is a point from the practical side of things. Suppose you are transmitting the baseband signal to a receiver, say your friends phone. Just like you there will be thousands of people in the city using their mobile phones. There is no way to tell such signals apart and they will interfere with each other leading to a lot of noise in the system and a very bad output. By using a carrier wave of high frequencies and allotting a band of frequencies to each message, there is no mixing up of signals and the received signals are absolutely perfect.

There are three types of Modulation:

Amplitude Modulation

Frequency Modulation

Phase Modulation

Established in 2000, the Soukacatv.com (DSW) main products are modulators both in digital and analog modulators, amplifier and combiner. We are the leading communication supplier in manufacturing the headend system in China. Our 16 in 1 and 24 in 1 now are the most popular products all over the world. For more, please access to https://www.soukacatv.com/.

Source：byjus

#HDMI encoder modulatorencoder modulator16in1 digital headendmodulatorHD RF modulatorSOUKAsoukacatv

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soukacatv · 6 years ago

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【Single Channel Modulator For Hotel Cable System at Soukacatv.com】The SK-963A is a cost-saving RF modulator. It's fixed channel and adjacent one with professional performance. It's with SAW flitering and available for any cable channel from 45-230MHz. This unit offers high performance, EXTREMELY LOW COST and compact design.For more, please access to https://www.soukacatv.com/single-channel-modulator-for-hotel-cable-system_p12.html.

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soukacatv · 7 years ago

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How Does a Hotel TV System Work? | Soukacatv.com

Hospitality TV services are more than just a way to provide entertainment options for hotel guests. Cable TV providers for hotels typically offer solutions that include interactive services (and in some cases, business services) for people who need to stay connected while on-the-go. TV hotel connections are more than just modified business or consumer-grade solutions. They're custom built from the ground up to offer the type of experience your guests won't be able to find anywhere else.

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https://www.soukacatv.com/.

TV Systems for Hotels: Breaking It Down

In a traditional setting, every television in a building that you would want to provide cable TV service to would need to be connected to a set top box of some kind. Cable companies send audio and video information into the building to the box and the box passes it on to your TV.

In a place like a hotel with hundreds of TVs, this would be prohibitively expensive. Because of this, hotel TV systems hook each TV up to a central "stack" of boxes located elsewhere in the building. Each box is always playing one channel and whenever a guest switches to that channel, they access the feed from the box in question.

Most hotel TV systems use either satellite TV or cable TV companies to provide content for their guests. Things like picture quality, channel availability (including both SD and HD channels) and whether HD is defined as 720p or 1080p will all vary depending on the provider in question.

What is Pro:Idiom?

These are sometimes referred to as Pro:Idiom TV services because of the advanced level of encryption that they provide. Pro:Idiom encryption allows for the delivery of high definition digital television and video content on demand, and in a highly secure way. This is often required by pay TV services like HBO, Showtime or even ESPN before they will allow their signal to be used in a business such as a hotel.

Pro:Idiom technology is what eliminates the need to use set top boxes, as the central decoder in a hotel room decrypts the video from the received feed and re-encodes it for more secure delivery to the specialized TV sets in each room of the hotel.

Why Choose Cable One Business for Hotel or Hospitality TV?

What About Hotel IPTV (Internet Protocol Television) Systems?

IPTV hotel solutions are the natural evolution of this concept. Instead of using coaxial cables to deliver television signals, hotel IPTV systems allow audio and video information to be transmitted over the same cables used to deliver the internet connection to an environment. This is often referred to as Internet Protocol Television (IPTV) according to EngineersGarage.

The major advantage of this, is that all digital services can be integrated from phone to internet to television and more, thus creating a more reliable and unified experience. Cable companies offer solutions that allow hospitality establishments to provide a wide range of services beyond traditional television content, including but not limited to:

Local news and weather information

Information about local attractions and points of interest

More advanced, interactive hotel services

Video games

Internet-connected applications

Movie rental services

An ordering portal for hotel amenities and more

Established in 2000, the Soukacatv.com (DSW) main products are modulators both in digital and analog modulators,amplifier and combiner. We are the leading communication supplier in manufacturing the headend system in China. Our 16 in 1 and 24 in 1 now are the most popular products all over the world. For more, please access to https://www.soukacatv.com/.

Source: https://business.cableone.net/business-resources/industry-specific/how-hotel-tv-system-works

#HDMI encoder modulatorencoder modulator16in1 digital headendmodulatorHD RF modulatorSOUKAsoukacatv

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soukacatv · 7 years ago

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Comparison of Hospitality Industry CATV vs MATV vs IPTV Distribution System | Soukacatv.com

Few of the essential difference between MATV, CATV and IPTV are explained here below:

MATV (Master Antenna TV). Master Antenna Television or MATV, describes an analog cabling network which is used to distribute various television signals throughout a facility. With the installation of multiple satellite dishes, for centrally subscribing and distribution of any channel, from any part of the world (both Pay and Free TV services) can be delivered locally using the technology popularly termed as SMATV or Satellite Master

CATV (Cable TV). CATV is nothing but the home-to-home Cable TV delivery using traditional coaxial cable connection to each of the residential premises to distribute TV from a central point or head end. CATV services are more or less irrelevant for large Hospitality properties, since majority of their clients may not require local channels.

Antenna TV system. Thru installing MATV/SMATV capture and distribution infrastructure (popularly named as ‘headend”), the property owner provides each room with a Set Top Box (STB) provided by the broadcaster, which is normally housed centrally at the headend room to avoid accidental mistuning of channels by the guests. Each channel is modulated and distributed through the cabling network. Only a TV with remote is required in each room, and the entire channel array, shall be displayed locally. The traditional analog headend system used to have several noise-generating components that affect the signal levels resulting in distortions in end-user TV signals like ghost images, snow, etc. Another issue of analog headend used to its limited channel capacity. While, the maximum theoretical limit is 106 channels, practically, it never used to exceed 80 channels per system.

Digital Video Broadcast SMATV. The above indicated drawbacks have been corrected in MATV systems based on Digital Headend. Poor signal quality and 80-channel limitations have easily been resolved by converting the TV signal transmission from analog to digital (DVB). Using DVB set-top boxes, each channel is converted to digital RF into AV or HDMI, which is fed directly to the AV or HDMI port of the TV. However, improper selection and sizing of these headend or its encoders can result in pixelisation and garbled TV picture. However, There is a significant cost in converting feed from analog to digital for encoders, QAM’s, etc. Local CATV services usually beams only local TV channels. Major benefit of SMATV over CATV is that, you can stream any TV services from any part of the world to your foreign guests/visitors.

IPTV (Internet Protocol TV). IPTV is when the media-to-broadcast content is Ethernet. Using large internet bandwidth, various broadcasting contents like TV, telephone, signage, video on demand, high speed internet etc can be delivered to end-user using a single UTP cable. Also, IPTV is a two-way communication. This means a hotel guest can communicate to the main hotel server to retrieve information like on-spot bill, room service ordering, laundering, car rental bookings, and messaging. The possibilities of IPTV are almost endless. For eg: Menu cards can be translated into various international languages, to help the guests know about any dish that they wish to order. It can be in terms of calorific value, feel and look of a dish, preparation time and method. Further, centralized Remote management of set-top box of every room TV is possible. Each set-top box is individually addressable for any specific guest message or function.

Importance of IPTV Sizing. Content delivery of IPTV requires right infrastructure planning. Such infra requires factoring of various operational requirements such as dissemination of number channels, services that are to be delivered, level of interactivity etc. Also, need to consider the convergence requirements of the project; say, the Data network, high speed internet, telephone services, signage, conferencing services etc shall share the same media, which will have tremendous Return of Investment (RoI). Towards this, only enterprise grade network hardware, having support to advanced streaming protocols are to be used on the network and are critical to handle the requisite "speed", "compression", “buffering”, “data processing thruput”, etc for a quality IPTV/Convergence infrastructure. Setting up of two parallel networks for IPTV and other IP services is not a good planning and is not going to be cost-effective.

The above aspects have been tabulated for the Busy-Eyes below:-

Established in 2000, the Soukacatv.com (DSW) main products are modulators both in digital and analog modulators,amplifier and combiner. We are the leading communication supplier in manufacturing the headend system in China. Our 16 in 1 and 24 in 1 now are the most popular products all over the world. For more, please access to https://www.soukacatv.com/.

Source: https://www.linkedin.com/pulse/catv-vs-matv-iptv-distribution-system-comparison-cdr-jacob-koottummel

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soukacatv · 7 years ago

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How Digital Television Works? To know how analog TV works | Soukacatv.com

If you've looked at television sets at any of the big electronics retailers in the United States lately, you know that digital TV, or DTV, is a big deal right now. Most stores have whole areas devoted to digital TV sets. You're also hearing a lot about four other topics:

· HDTV and HDTV broadcasts

· Digital satellite services

· Digital cable

· DVDs and DVD players

Unless you are among the people in the United States who have purchased a DTV set, what you have in your living room is a normal analog TV that seems to be working just fine despite all the hype. Most people, faced with this level of product proliferation, can only ask, "What the heck is going on here?!"

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On June 12, 2009, television stations in the United States completed the transition from analog to digital broadcasting. Consumers receiving local television signals over analog antennas now must use converter boxes to receive programming on their TVs. This deadline was pushed back several times in the last few years because of both broadcasters' and consumers' inability to meet the FCC's criteria for a successful transition to digital broadcasting.

The change was last scheduled to take place on Feb. 17, 2009, but was pushed back one final time to allow more people to purchase new TVs or converter boxes to allow them to make the transition. Some stations, however, switched to digital broadcasting in February 2009 anyhow because they'd already contracted time to broadcast on digital transmitters and staying analog would require a costly budgetary adjustment.

In this article, we will explore the world of digital television so that you can understand exactly what is going on in this medium.

Understanding Analog TV

To understand digital TV, it's helpful to understand analog TV so that you can see the differences. (If you've read How Television Works, then you know how analog TV works).

The analog TV standard has been in use in the United States for about 50 years. To review quickly, here are the basics of analog television transmission:

· A video camera takes a picture of a scene. It does this at a frame rate of 30 frames per second.

· The camera rasterizes the scene. That is, the camera turns the picture into rows of individual dots called pixels. Each pixel is assigned a color and intensity.

· The rows of pixels are combined with synchronization signals, called horizontal sync and vertical sync signals, so that the electronics inside a TV set will know how to display the rows of pixels.

This final signal, containing the color and intensity of each pixel in a set of rows, along with horizontal and vertical sync signals, is called a composite video signal. Sound is completely separate. When you look on the back of your VCR and you see the yellow plug, that's the plug for composite video. Sound is either a white plug (on VCRs that do not handle stereo sound) or a red plug and a white plug (on VCRs that do handle stereo).

There are lots of different things you can do with a composite video signal and a sound signal. Here are just a few:

· You can broadcast them as radio waves. When you attach an antenna to your TV set and pick up local stations for free, you're receiving broadcast television from local TV stations.

· You can record them with a VCR.

· You can transmit them through a cable TV system along with hundreds of other composite signals.

Many different kinds of equipment understand composite video signals.

When a composite video signal is broadcast over the airwaves by a TV station, it happens on a specific frequency. In the United States, we know these frequencies as VHF channels 2 through 13 and UHF channels 14 through 83.

The composite video signal is transmitted as an AM signal and the sound as an FM signal on these channels. See How TV Works for details on transmission, and How Radio Works for details on AM and FM. The FCC allocated three bands of frequencies in the radio spectrum, chopped into 6-MHz slices, to accommodate these TV channels:

· 54 to 88 MHz for Channels 2 to 6

· 174 to 216 MHz for Channels 7 through 13

· 470 to 890 MHz for UHF Channels 14 through 83

When your VCR wants to display its signal on a normal analog TV, it takes the composite video signal and the sound signal off the tape and then modulates those signals onto a 60-MHz (channel 3) or 66-MHz (channel 4) carrier, just like a TV station would. Instead of broadcasting it, however, the VCR sends it straight to the TV. A cable box or satellite box does the same thing.

Right now you hear a lot about "digital satellite systems" and "digital cable systems." The set-top box receives a digital signal from the satellite or cable; the box then converts that signal to an analog signal and sends it to your analog TV. That's why if you're a digital cable or satellite TV subscriber, your provider probably told you that the June 2009 DTV transition wouldn't require you to buy new equipment.

True digital TV, on the other hand, is completely digital and involves:

· Digital cameras working at a much higher resolution than analog cameras

· Digital transmission

· Digital display at a much higher resolution

You can see the difference in resolution in the next section.

What's Wrong with Analog TV?

If you currently have an analog TV, and it works fine with broadcast TV, cable TV, VCRs, satellite TV, camcordersand so on, an obvious question would be, "What's wrong with analog TV?"

The main problem is resolution.

· The resolution of the TV controls the crispness and detail in the picture you see.

· The resolution is determined by the number of pixels on the screen.

· An analog TV set can display 525 horizontal lines of resolution every 30th of a second. In reality, however, an analog TV displays half of those lines in a 60th of a second, and then displays the other half in the next 60th, so the whole frame is updated every 30th of a second. This process is called interlacing.

That's been the way TV works for years. But now we've used to looking at computer monitors and expect much better resolution. The lowest-resolution computer monitor displays 640 x 480 pixels. Because of the interlacing, the effective resolution of a TV screen is perhaps 512 x 400 pixels.

So the worst computer monitors you can buy have more resolution than the best analog TV set; and the best computer monitors are able to display up to 10 times more pixels than that TV set. There is simply no comparison between a computer monitor and an analog TV in terms of detail, crispness, image stability and color. If you look at a computer monitor all day at work, and then go home and look at a TV set, the TV set can look very fuzzy.

The drive toward digital TV is fueled by the desire to give TV the same crispness and detail as a computer screen. If you have ever looked at a true digital TV signal displayed on a good digital TV set, you can certainly understand why -- the digital version of TV looks fantastic! There's no comparison. With 10 times more pixels on the screen, all displayed with digital precision, the picture is incredibly detailed and stable.

It's hard to convey the difference between a DTV signal and an analog signal without an actual demonstration, but here's a static comparison that can help you understand the idea. Below is a picture of an odometer:

This is a nice, crisp picture. Let's assume that this picture is being displayed on a good digital TV so that this is what you actually see. The following photo shows you what you would see on an analog TV:

You can see that the analog TV picture is much fuzzier than the digital TV image. Look, for example, at the teeth on the gears. There's a significant difference in picture quality that's even more obvious when the image is moving. It is that quantitative difference that drives the interest in digital TV. And as if the incredible picture weren't enough, digital TV also offers much better sound.

TV Goes Digital

The term "digital TV" is used in many different ways right now, depending on whom you're talking to. There's also the term "HDTV," which is the most advanced form of digital TV in use in the United States. The reason it gets confusing is because digital TV in the United States combines three different ideas.

The first idea that is new to digital TV is the digital signal.

Analog TV started as a broadcast medium. TV stations set up antennas and broadcast radio signals to individual communities. You can attach an antenna to your TV and pick up channels 2 through 83 for free. What you receive, as described earlier, is a single, analog composite video signal and a separate sound signal.

Digital TV started as a free broadcast medium as well. For example, in San Jose, Calif., you can tune in to about a dozen different commercial digital TV stations if you have a digital TV receiver and an antenna. The FCC gave television broadcasters a new frequency to use for their digital broadcasts, so until the digital transition is complete, each broadcaster has an analog TV channel and a digital TV channel. The digital channel carries a 19.39-megabit-per-second stream of digital data that your digital TV receives and decodes.

Each broadcaster has one digital TV channel, but one channel can carry multiple sub-channels if the broadcaster chooses that option. Here's how it works:

On its digital channel, each broadcaster sends a 19.39-megabit-per-second (Mbps) stream of digital data. Broadcasters have the ability to use this stream in several different ways. For example:

· A broadcaster can send a single program at 19.39 Mbps.

· A broadcaster can divide the channel into several different streams (perhaps four streams of 4.85 Mbps each). These streams are called sub-channels, and this type of broadcasting is called multicasting. For example, if the digital TV channel is channel 53, then 53.1, 53.2 and 53.3 could be three sub-channels on that channel. Each sub-channel can carry a different program.

The reason that broadcasters can create sub-channels is because digital TV standards allow several different formats. Broadcasters can choose between three formats:

· 480i - The picture is 704x480 pixels, sent at 60 interlaced frames per second (30 complete frames per second).

· 480p - The picture is 704x480 pixels, sent at 60 complete frames per second.

· 720p - The picture is 1280x720 pixels, sent at 60 complete frames per second.

· 1080i - The picture is 1920x1080 pixels, sent at 60 interlaced frames per second (30 complete frames per second).

· 1080p - The picture is 1920x1080 pixels, sent at 60 complete frames per second.

(The "p" and "i" designations stand for "progressive" and "interlaced." In a progressive format, the full picture updates every 60th of a second. In an interlaced format, half of the picture updates every 60th of a second.)

The 480p and 480i formats are called the SD (standard definition) formats, and 480i is roughly equivalent to a normal analog TV picture. When analog TV shows are upconverted and broadcast on digital TV stations, they're broadcast in 480p or 480i.

The 720p, 1080i and 1080p formats are HD (high definition) formats. When you hear about "HDTV," this is what is being discussed -- a digital signal in the 720p, 1080i or 1080p format.

Finally, the HD formats of digital TV have a different aspect ratio than analog TVs. An analog TV has a 4:3 aspect ratio, meaning that the screen is 4 units wide and 3 units high. For example, a "25-inch diagonal" analog TV is 15 inches high and 20 inches wide. The HD format for digital TV has a 16:9 aspect ratio, as shown below:

The type of signal, format and aspect ratio have all changed in the process of converting from analog TV to digital TV in the United States.

Digital Compression

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The idea of sending multiple programs within the 19.39-Mbps stream is unique to digital TV and is made possible by the digital compression system being used. To compress the image for transmission, broadcasters use MPEG-2 compression, and MPEG-2 allows you to pick both the screen size and bit rate when encoding the show. A broadcaster can choose a variety of bit rates within any of the three resolutions.

You see MPEG-2 all the time on the Web on Web sites that offer streaming video. For example, if you go to iFilm.com, you will find that you can view streaming video at 56 kilobits per second (Kbps), 200 Kbps or 500 Kbps. MPEG-2 allows a technician to pick any bit rate and resolution when encoding a file.

There are many variables that determine how the picture will look at a given bit rate. For example:

· If a station wants to broadcast a sporting event (where there is lots of movement in the scene) at 1080i, the entire 19.39 megabits per second is needed to get a high-quality image.

· On the other hand, a newscast showing a newscaster's head can use a much lower bit rate. A broadcaster might transmit the newscast at 480p resolution and a 3-Mbps bit rate, leaving 16.39 Mbps of space for other sub-channels.

It's very likely that broadcasters will send three or four sub-channels during the day and then switch to a single high-quality show that consumes the entire 19.39 Mbps at night. Some broadcasters are also experimenting with 1- or 2-Mbps data channels that send information and Web pages along with a show to provide additional information.

Buying a Digital TV Set

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If you go to an electronics store today to buy a new TV set, there are four types of sets that you will see on the shelf:

· Analog TV sets

· Digital-ready sets - They should be identified as standard definition (SDTV) sets. These TVs are normally 480p displays with a digital tuner built in. The problem with these sets is that their maximum resolution is the low 480p SD resolution, so if you want to watch high-definition TV, you won't be able to use these sets.

· HDTV-ready sets - These sets are essentially monitors able to display 1080i/p resolution in the 16:9 aspect ratio. They may or may not have tuners built in.

· Integrated HDTV sets - These sets have a digital tuner for broadcast DTV signals integrated into an HDTV display. With the standards changing so much, you may end up paying for an integrated tuner that becomes obsolete.

The preferred way to handle HDTV is to purchase the components separately:

· A 16:9 HDTV display capable of 720p and 1080i/p resolution

· A digital receiver

· An antenna

Since the HDTV display will be the most expensive piece and will likely last 10 years or more, buying the components in this way allows you to change the receiver if you need to. There are currently three types of receivers:

1. You can purchase a set-top box and a Yagi antenna to receive broadcast HDTV signals.

2. You can purchase a set-top box and a small satellite dish to receive HDTV signals from a satellite.

3. You can purchase a board for your computer that lets you use your hard disk as an HDTV storage device, along with a Yagi antenna, and use it to receive signals on both your computer monitor and your HDTV display.

Source: electronics.howstuffworks

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soukacatv · 7 years ago

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Digital vs Analog TV comparison | Soukacatv.com

Digital vs Analog? Analog vs Digital? What’s the big deal about the switch in signal to your TV?

There have been no bigger advancements in technology over the last 20 years then what is happening in the television industry. Only 10 or so years ago the price of flat screen TVs were astronomical and were only affordable by wealthy individuals. Fast forward to today’s retail economy and a quality flat screen TV can be found for well under $500. With these new TVs comes the world of high definition that broadcasts sporting events, movies and television shows with a much clearer picture then televisions of the past. With the broadcast of events in high definition (HD) comes the need for a better broadcasting system, this is where digital TV service has come in and revolutionized the cable TV industry.

Let’s take a further look into the Digital vs Analog TV comparison

Advancements in Technology

Up until the past few years, commercial televisions sets have all worked from receiving analog signals. With analog, televisions receive radio frequencies that were sent out from a variety of TV stations. Each TV station emits a frequency that corresponds to a channel number. With this technology analog TV sets received a constant signal to their antenna that would change when they switched channels.

On the other hand, digital signals work much like computers. Instead of using a radio frequency, the digital signal is sent out in a series of 1s and 0s. Any television with a digital tuner will receive this information and will generate the picture and sound onto their TV.

Quality of Programming

Every one of us who are older than 30 can remember their analog signal from when they were young. While some of the higher quality channels came in with good picture quality most of the time, there were many channels that had the snowy or fuzzy look on the TV screen. This problem has to do with the type of signal transmitted from the different stations. With the analog signal the quality of the signal was determined by the strength of the analog signal, the antenna’s proximity to the television station and possible obstructions depending on where your TV was located. A weak analog signal constituted a poor picture for the viewer.

With the digital signal, things like proximity and obstructions will not have any effect on the picture. With a binary signal, the broadcast is not only higher quality then the analog signal but the picture will not have has any of the graininess of the analog picture. The only problem that a digital picture may get is a momentary freezing of the picture if the signal gets interrupted. While this was more of a problem with the early digital ready TVs, this technology has been improved upon in the last couple of years to almost be non-existent.

High Definition (HD) TVs

One of the main reasons that the analog vs digital programming has become such a discussed technology is the recent availability of HD TVs to the general population. Sporting events, movies and cable shows show the true value of digital programming as their HD channels are a clear upgrade from “regular” cable channels. From their initial release to present day the pricing of high definition televisions has dropped tremendously. For instance a 32” TV may have costs $2,000 dollars in 2003 and now the same size 32” LED TV with much better features can be found for under $400. With these pricing changes businesses can now afford to add digital ready TVs at low costs.

Overall

Digital vs analog is something that will not even be debated 10 years from now as technology will keep pushing analog technology further and further back. As of 2013, most satellite TV providers will no longer offer analog channels. With this change more businesses will look to add the LED, commercial grade TVs to their businesses while sending the old analog TVs to the recycle bin.

Established in 2000, the Soukacatv.com (DSW) main products are modulators both in digital

and analog modulators, amplifier and combiner. We are the leading communication supplier in

manufacturing the headend system in China. Our 16 in 1 and 24 in 1 now are the most popular

products all over the world. For more, please access to https://www.soukacatv.com/.

Source: seniortv

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soukacatv · 7 years ago

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【High Output Level Agile Modulator For Cable System at Soukacatv.com】The SK-4000M is commercial grade, SAW filtered, freuency agile modulator specifically designed to meet the hightes CATV performance standards. All channels are easily selected using front panel buttons and verified with an EASY-TO-READ LED channel display.For more, please access tohttps://www.soukacatv.com/high-output-level-agile-modulator-for-cable-system_p29.html

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soukacatv · 7 years ago

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Brief Introduction of Cable Television: Definition, History and Development | Soukacatv.com

Cable television is a way of letting people watch television without having to get signals from an antenna. The television signals are brought to the television through a coaxial cable. People usually have to pay to subscribe to cable television. With cable television, people can watch hundreds of television channels carrying many television shows. Usually some of these are television stations and others are made for the cable companies.

Cable TV is provided by many carriers in across with world. Some of those carriers in the United States are: AT&T U-Verse, CableVision, Comcast, Cox Communications, SuddenLink, Time Warner Cable and Verizon

Another method of subscription television is by Satellite television, especially in places where cable TV is not available.

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Cable television is a system of delivering television programming to consumers via radio frequency (RF) signals transmitted through coaxial cables, or in more recent systems, light pulses through fiber-optic cables. This contrasts with broadcast television (also known as terrestrial television), in which the television signal is transmitted over the air by radio wavesand received by a television antenna attached to the television; or satellite television, in which the television signal is transmitted by a communications satellite orbiting the Earth and received by a satellite dish on the roof. FM radio programming, high-speed Internet, telephone services, and similar non-television services may also be provided through these cables. Analog television was standard in the 20th century, but since the 2000s, cable systems have been upgraded to digital cable operation.

A "cable channel" (sometimes known as a "cable network") is a television network available via cable television. When available through satellite television, including direct broadcast satellite providers such as DirecTV, Dish Network and Sky, as well as via IPTV providers such as Verizon FIOS and AT&T U-verse is referred to as a "satellite channel". Alternative terms include "non-broadcast channel" or "programming service", the latter being mainly used in legal contexts. Examples of cable/satellite channels/cable networks available in many countries are HBO, Cinemax, MTV, Cartoon Network, AXN, E!, Fox Life, Discovery Channel, Canal+, Eurosport, Fox Sports, Disney Channel, Nickelodeon, CNN International, ESPN, GMA Pinoy TV and The Filipino Channel.

The abbreviation CATV is often used for cable television. It originally stood for Community Access Television or Community Antenna Television, from cable television's origins in 1948. In areas where over-the-air TV reception was limited by distance from transmitters or mountainous terrain, large "community antennas" were constructed, and cable was run from them to individual homes. The origins of cable broadcasting for radio are even older as radio programming was distributed by cable in some European cities as far back as 1924.

History in North America

Cable television began in the United States as a commercial business in 1950, although there were small-scale systems by hobbyists in the 1940s.

The early systems simply received weak (broadcast) channels, amplified them, and sent them over unshielded wires to the subscribers, limited to a community or to adjacent communities. The receiving antenna would be higher than any individual subscriber could afford, thus bringing in stronger signals; in hilly or mountainous terrain it would be placed at a high elevation.

At the outset, cable systems only served smaller communities without television stations of their own, and which could not easily receive signals from stations in cities because of distance or hilly terrain. In Canada, however, communities with their own signals were fertile cable markets, as viewers wanted to receive American signals. Rarely, as in the college town of Alfred, New York, U.S. cable systems retransmitted Canadian channels.

Although early (VHF) television receivers could receive 12 channels (2-13), the maximum number of channels that could be broadcast in one city was 7: channels 2, 4, either 5 or 6, 7, 9, 11 and 13, as receivers at the time were unable to receive strong (local) signals on adjacent channels without distortion. (There were frequency gaps between 4 and 5, and between 6 and 7, which allowed both to be used in the same city).

As equipment improved, all twelve channels could be utilized, except where a local VHF television station broadcast. Local broadcast channels were not usable for signals deemed to be priority, but technology allowed low-priority signals to be placed on such channels by synchronizing their blanking intervals. Similarly, a local VHF station could not be carried on its broadcast channel as the signals would arrive at the TV set slightly separated in time, causing "ghosting".

The bandwidth of the amplifiers also was limited, meaning frequencies over 250 MHz were difficult to transmit to distant portions of the coaxial network, and UHF channels could not be used at all. To expand beyond 12 channels, non-standard "midband" channels had to be used, located between the FM band and Channel 7, or "superband" beyond Channel 13 up to about 300 MHz; these channels initially were only accessible using separate tuner boxes that sent the chosen channel into the TV set on Channel 2, 3 or 4.

Before being added to the cable box itself, these midband channels were used for early incarnations of pay TV, e.g. The Z Channel(Los Angeles) and HBO but transmitted in the clear i.e. not scrambled as standard TV sets of the period could not pick up the signal nor could the average consumer `de-tune' the normal stations to be able to receive it.

Once tuners that could receive select mid-band and super-band channels began to be incorporated into standard television sets, broadcasters were forced to either install scrambling circuitry or move these signals further out of the range of reception for early cable-ready TVs and VCRs. However, once all 181 allocated cable channels had been incorporated, premium broadcasters were left with no choice but to scramble.

Unfortunately for pay-TV operators, the descrambling circuitry was often published in electronics hobby magazines such as Popular Science and Popular Electronics allowing anybody with anything more than a rudimentary knowledge of broadcast electronics to be able to build their own and receive the programming without cost.

Later, the cable operators began to carry FM radio stations, and encouraged subscribers to connect their FM stereo sets to cable. Before stereo and bilingual TV sound became common, Pay-TV channel sound was added to the FM stereo cable line-ups. About this time, operators expanded beyond the 12-channel dial to use the "midband" and "superband" VHF channels adjacent to the "high band" 7-13 of North American television frequencies. Some operators as in Cornwall, Ontario, used a dual distribution network with Channels 2-13 on each of the two cables.

During the 1980s, United States regulations not unlike public, educational, and government access (PEG) created the beginning of cable-originated live television programming. As cable penetration increased, numerous cable-only TV stations were launched, many with their own news bureaus that could provide more immediate and more localized content than that provided by the nearest network newscast.

Such stations may use similar on-air branding as that used by the nearby broadcast network affiliate, but the fact that these stations do not broadcast over the air and are not regulated by the FCC, their call signs are meaningless. These stations evolved partially into today's over-the-air digital subchannels, where a main broadcast TV station e.g. NBS 37* would – in the case of no local CNB or ABS station being available – rebroadcast the programming from a nearby affiliate but fill in with its own news and other community programming to suit its own locale. Many live local programs with local interests were subsequently created all over the United States in most major television markets in the early 1980s.

This evolved into today's many cable-only broadcasts of diverse programming, including cable-only produced television moviesand miniseries. Cable specialty channels, starting with channels oriented to show movies and large sporting or performance events, diversified further, and "narrowcasting" became common. By the late 1980s, cable-only signals outnumbered broadcast signals on cable systems, some of which by this time had expanded beyond 35 channels. By the mid-1980s in Canada, cable operators were allowed by the regulators to enter into distribution contracts with cable networks on their own.

By the 1990s, tiers became common, with customers able to subscribe to different tiers to obtain different selections of additional channels above the basic selection. By subscribing to additional tiers, customers could get specialty channels, movie channels, and foreign channels. Large cable companies used addressable descramblers to limit access to premium channels for customers not subscribing to higher tiers, however the above magazines often published workarounds for that technology as well.

During the 1990s, the pressure to accommodate the growing array of offerings resulted in digital transmission that made more efficient use of the VHF signal capacity; fibre optics was common to carry signals into areas near the home, where coax could carry higher frequencies over the short remaining distance. Although for a time in the 1980s and 1990s, television receivers and VCRs were equipped to receive the mid-band and super-band channels. Due to the fact that the descrambling circuitry was for a time present in these tuners, depriving the cable operator of much of their revenue, such cable-ready tuners are rarely used now - requiring a return to the set-top boxes used from the 1970s onward.

The conversion to digital broadcasting has put all signals - broadcast and cable - into digital form, rendering analog cable television service mostly obsolete, functional in an ever-dwindling supply of select markets. Analog television sets are still[when?]accommodated, but their tuners are mostly obsolete, oftentimes dependent entirely on the set-top box.

Deployments by continent

Cable television is mostly available in North America, Europe, Australia, South Asia and East Asia, and less so in South America and the Middle East. Cable television has had little success in Africa, as it is not cost-effective to lay cables in sparsely populated areas. So-called "wireless cable" or microwave-based systems are used instead.

Cable television, generally, any system that distributes television signals by means of coaxial or fibre-optic cables. The term also includes systems that distribute signals solely via satellite. Cable-television systems originated in the United States in the late 1940s and were designed to improve reception of commercial network broadcasts in remote and hilly areas. During the 1960s they were introduced in many large metropolitan areas where local television reception is degraded by the reflection of signals from tall buildings. Commonly known as community antenna television (CATV), these cable systems use a “community antenna” to receive broadcast signals (often from communications satellites), which they then retransmit via cables to homes and establishments in the local area subscribing to the service. Subscribers pay a specified monthly service charge in addition to an initial installation fee.

Established in 2000, the Soukacatv.com (DSW) main products are modulators both in digital and analog modulators,amplifier and combiner. We are the leading communication supplier in manufacturing the headend system in China. Our 16 in 1 and 24 in 1 now are the most popular products all over the world. For more, please access to https://www.soukacatv.com/.

Source: From Wikipedia, the free encyclopedia

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soukacatv · 7 years ago

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【Agile Audio/Video Modulator with SAW filter at Soukacatv.com】The SK-3000M is cost-saving grade, SAW filtered, freuency agile modulator specifically designed to meet the hightes HOTEL performance standards. All channels are easily selected using front panel buttons and verified with an EASY-TO-READ LED channel display.For more, please access to https://www.soukacatv.com/agile-audio-video-modulator-with-saw-filter_p30.html

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soukacatv · 6 years ago

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Brief Introduction about the Definition and Characteristics of Digital Signal | Soukacatv.com

A digital signal refers to an electrical signal that is converted into a pattern of bits. Unlike an analog signal, which is a continuous signal that contains time-varying quantities, a digital signal has a discrete value at each sampling point. The precision of the signal is determined by how many samples are recorded per unit of time. For example, the illustration below shows an analog pattern (represented as the curve) alongside a digital pattern (represented as the discrete lines).

A digital signal is easily represented by a computer because each sample can be defined with a series of bits that are either in the state 1 (on) or 0 (off). Digital signals can be compressed and can include additional information for error correction.

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Characteristics of Digital Signals 1. Bit interval It is the time required to send one single bit

2. Bit rate (i) It refers to the number of bit intervals in one second. (ii) Therefore bit rate is the number of bits sent in one second as shown in fig. (iii)Bit rate is expressed in bits per second (bps). (iv)Other units used to express bit rate are Kbps, Mbps and Gbps. 1 kilobit per second (Kbps) = 1,000 bits per second 1 Megabit per second (Mbps) = 1,000,000 bits per second 1 Gigabit per second (Gbps) = 1,000,000,000 bits per second

Advantages of Digital Signals Digital Data - Digital transmission certainly has the advantage where binary computer data is being transmitted. The equipment required to convert digital data to analog format and transmitting the digital bit streams over an analog network can be expensive, susceptible to failure, and can create errors in the information.

Compression - Digital data can be compressed relatively easily, thereby increasing the efficiency of transmission. As a result, substantial volumes of voice, data, video and image information can be transmitted using relatively little raw bandwidth.

Security - Digital systems offer better security. While analog systems offer some measure of security through the scrambling of several frequencies. Scrambling is fairly simple to defeat. Digital information, on the other hand, can be encrypted to create the appearance of a single, pseudorandom bit stream. Thereby, the true meaning of individual bits, sets of bits, or the total bit stream cannot be determined without having the key to unlock the encryption algorithm employed.

Quality - Digital transmission offers improved error performance (quality) as compared to analog. This is due to the devices that boost the signal at periodic intervals in the transmission system in order to overcome the effects of attenuation. Additionally, digital networks deal more effectively with noise, which always is present in transmission networks.

Cost - The cost of the computer components required in digital conversion and transmission has dropped considerably, while the ruggedness and reliability of those components has increased over the years.

Upgradeability - Since digital networks are comprised of computer (digital) components, they are relatively easy to upgrade. Such upgrading can increase bandwidth, reduces the incidence of error and enhance functional value. Some upgrading can be effected remotely over a network, eliminating the need to dispatch expensive technicians for that purpose.

Management - Generally speaking, digital networks can be managed much more easily and effectively due to the fact that such networks consist of computerized components. Such components can sense their own level of performance, isolate and diagnose failures, initiate alarms, respond to queries, and respond to commands to correct any failure. Further, the cost of these components continues to drop.

Source: ecomputernotes

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