Multiplexer multiplexer
is an
device,
which
selects one of several inputs and
connects it to its outlet.
Multiplexer
(from
english
multiplex
–
multiple) is a telecommunication device,
combining several data streams or channels
into one output signal (group stream).

Definitions

The multiplexer samples one of several inputs and
connects it to its output, depending on the state of the binary
code.
Multiplexer - binary controlled signal switch
and having multiple inputs and one output. The one connected to the output
an input whose number corresponds to a binary code.
Or a multiplexer is a device that converts parallel code into
consistent.

The multiplexer has several information inputs (D0, D1, ...), address inputs (A0 A1, ...), an input for signaling C and

one output Q.

Each data input of the multiplexer
a number called an address is assigned.
When a signal is applied to input C, the multiplexer selects
one of the inputs, the address of which is set in binary
code at the address inputs, and connects it to the output.

Multiplexer

Thus, supplying the address inputs with the addresses of various
information inputs, you can transfer digital
signals from these inputs to output Q.
The number of information inputs ninf and the number of address
inputs nadr are connected by the ratio ninf = 2nadr.

The multiplexer can have, for example, 16 inputs and
one way out.
If 16 sources are connected to these inputs
digital signals - generators of serial
digital words, then bytes from any of them can
transmit to the only way out.
To select any of the 16 channels, you must have 4
selection inputs (24 = 16), to which a binary
channel address.

For data transmission from channel 9 at the inputs
selection, you must set the code 1001.
Multiplexers are often called selectors or
selectors-multiplexers.

Multiplexer Truth Table

Addressable
entrances
Signal C
Output
A1
A0
*
*
0
0
0
0
1
D0
0
1
1
D1
1
0
1
D2
1
1
1
D3

Example

For example, when setting the address AlA0 = ll2 = 310 to
output
Q
will
be transmitted
signal
information input with address 310, i.e. D3.

Control signal C

In the absence of a control signal (C = 0) communication
between information inputs and outputs
absent (Q = 0).
When a control signal (C = l) is applied to the output
transmitted
logical
level
Togo
from
information inputs Di, the number of which is i in
binary form is set at the address inputs.

Multiplexer functions

According to the truth table, you can write a logical expression for
output Q.
Boolean multiplexer expression (*)

Functioning diagram

Using multiplexers to synthesize combinational devices

Multiplexers can be used for synthesis
logical functions.
In this case, the number of elements used in the circuit is
(cases of integrated circuits) can be
significantly reduced.

Boolean multiplexer expression

The multiplexer boolean expression (*) contains members with
all combinations of address variables.
Therefore, if it is required to synthesize a function of three
variables f (x1, x2, x3), then two of these variables (for example, x1,
x2) can be fed to the address inputs A1, and A0, and the third x3 - to
information entrance.

Truth table

Functioning diagram

conclusions

on four-input multiplexers can be synthesized
any function of three variables,
on eight-input multiplexers - any function of four
variables, etc.

Implementation of LF in 4 variables

Demultiplexers

The demultiplexer has one information input and
multiple exits.
It is a device that carries out
switching the input to one of the outputs, which has
given address (number).
With their help signals from one information input
distributed in the required sequence over
multiple outputs.

With m address inputs, the demultiplexer can have
up to 2m outputs.
In the form of a microcircuit specially designed for
this, the demultiplexer is not implemented.
Demultiplexer
implemented
on
having an enable input E.
decoder,

An example of a decoder-based demultiplexer implementation is shown in the figure.

Symbolic representation of a demultiplexer with four outputs

Using a demultiplexer can
significantly simplify the construction
logical device with several
outputs on which various
logical functions of the same
variables.

Dual channel multiplexer

Implementation of a given function using a multiplexer

To implement the function on the multiplexer, it is necessary to apply to the information
input of multiplexer with number N is a signal whose value is
corresponding value of function F1, i.e. inputs with numbers 1, 2, 4, 5 should be
to give the level of logical zero, and to the rest - the level of logical units.
Build the diagram.

Develop, assemble and test the operation of a circuit based on an 8x1 multiplexer that implements a given logical function Y.

1.
Y = C'B '+ CA
2.
Y = B'A '+ C'B' + C'A '
3.
Y = C'B'A '+ CB'A + C'BA
4.
Y = CA + B'A '+ C'A'
5.
Y = AC + BA
6.
Y = C'A + B'A '+ C'B
7.
Y = C '+ AB' + AC
8.
Y = CBA + C'B'A '
9.
Y = AC + A'B'C
10.
Y = C '+ B'C + AB

Today, the purchase of additional equipment or special devices is quite an expensive pleasure. In order to save their financial costs, devices such as a multiplexer and a demultiplexer are often used, which are a kind of data selectors.

In the case of a multiplexer, it is possible to pass information from several inputs through one output. And the demultiplexer acts exactly the opposite - distributes the received data from one input to different outputs.

A multiplexer is a piece of equipment that contains several signal inputs, one or more control inputs, and only one common output. This device makes it possible to transfer a specific channel from one of the available inputs to a special and only output.

With all this, the input is selected by applying a certain combination of control signals. Most often, a multiplexer is needed where it is necessary to equip a large number of channels (signals) to transmit signals, but there is no money and technical equipment for this.

The efficiency of this type of device is based on the fact that the communication signal, even if it is one, is very often not applied to its full power. For this reason, there is extra room to run other streams of information on the same line.

Of course, if all these streams are launched in their original form and at the same time, then the output will be the usual jumble of information data, which will be practically impossible to decipher. Because of this, the multiplexer is produced by dividing information streams in a variety of ways.

Frequency banding is when all data streams are sent at the same time, but with different frequencies. There is no mixing of streams. In addition, it is possible to start streams in different timelines. The coding method is also especially popular. In this case, all streams are designated with special characters, encoded and sent simultaneously.

Multiplexers are classified according to several criteria: by the place of use or by their purpose, and so on.


 Communication line of multiplexer and demultiplexer

The main difference between multiplexers is how the signals are compressed into one continuous stream.

Multiplexing is of the following types:

  • temporary;
  • spatial type;
  • code;

As a rule, if the channels are wired, then the first two methods are relevant in the application, and all four options are used for wireless channels. Usually, when it comes to a multiplexer, it means a wired device.

For this reason, it is worthwhile to familiarize yourself in more detail with the frequency and time methods:

Multiplexing methods


To perform frequency multiplexing, it is necessary to define a certain frequency period for all streams. Before the process itself, it is necessary to move the spectrum of all channels that are included in the period of a different frequency, which will not intersect with other signals in any way. In addition, to ensure reliability, certain intervals are made between frequencies for additional protection. This method is used in both electrical and optical communication lines.

Temporary option


 Time division multiplexing and demultiplexing

There is a certain amount of time to transmit each signal in the continuous stream that comes in. In this case, the device has a special task - to ensure that the loops have access to the general redirection environment for flows that enter for a small time period.

At the same time, it is necessary to make sure that there is no undesirable overlap of channels on each other, which mixes information. To do this, use special intervals for protection, which are placed between these same channels.

This method is used, as a rule, for digital communication channels.

Classification of multiplexers

Multiplexers are of the following types:

  1. Terminal. They are placed at the ends of the connected lines.
  2. Input and output. Such devices are built into the break of connected lines in order to output certain signals from the continuous stream. With their help, you can do without expensive terminal-type multiplexers.

Also, multiplexers are classified in this way:

Analog multiplexers


Analog type switches are special analog-discrete elements. An analog key can be presented as a separate device. A set of this kind of keys, which work for a single output with sampling circuits of a certain key, is a special analog multiplexer. Analog equipment at each time period selects a specific input channel and directs it to a special device

Digital multiplexers


Digital equipment is divided into multiplexers of the second, first and other high levels. Digital multiplexers make it possible to receive digital signals from low-level devices. At the same time, you can write them down, form a high-level digital current. This way, the incoming streams are synchronized. It can also be noted that they have the same speeds.

Areas of use

Video multiplexers are used in television technology and various displays, in security video surveillance systems. Multiplexing is the basis for GSM communication and a variety of providers' input modems on the Internet. Also, these devices are used in GPS receivers, in broadband fiber-optic communication lines.

Multiplexers are used in various frequency dividers, special trigger elements, special shifting devices, and so on. They can be used to convert certain parallel binary code to serial.


 Optical multiplexer application diagram

Multiplexer structure

The multiplexer consists of a special decoder of the address of the input line of the channels, various schemes, including the combining scheme.

The structure of the multiplexer can be seen on the example of its general scheme. Logic input data is fed to the outputs of the switch, and then sent through it to the output. The words of the address channels are fed to the control input. The device itself may also have a special control input, which makes it possible to pass or not pass the input channel to the output.

There are types of multiplexers that have a tri-state output. All the nuances of the multiplexer operation depend on its model.

Demultiplexer

A demultiplexer is a logical device that is designed to freely switch the signal from one information input to one of the available information outputs. In fact, a demultiplexer is the opposite of a multiplexer.

During data transmission over a common signal with division along the time course, both the use of multiplexers and the use of demultiplexers are necessary, that is, a device with a reverse functional purpose. This device distributes information data from one signal among multiple data receivers.

A special difference of this type of device from multiplexers is that it is possible to ice a certain number of inputs into one without using additional circuits. But in order to increase the load of the microcircuit, it is recommended to install a special inverter at the output of the device to increase the input channel.

In the scheme of the simplest such device, a binary decoder is used for a specific output. It is worth noting that with a detailed study of the decoder, you can make the demultiplexer much easier. To do this, it is necessary to add another input to all logical elements that are part of the decoder structure. This structure is often called a decoder, which has a work permit input.

What should you look for when choosing a multiplexer?

  1. What cameras are used - black and white, color?
  2. The total number of cameras that can be connected to the device.
  3. Multiplexer type.
  4. Device resolution.
  5. The presence of a detector that determines the movement.
  6. Can a second monitor screen be connected?

When choosing a multiplexer or demultiplexer, it is necessary to take into account all the nuances and technical characteristics of the device.

Multiplexers are special network devices that are designed to transmit various streams of information at high speed. The transmission uses a single communication line. The transmitted information stream should have a low speed.

The use of multiplexers is an urgent, fast and economical measure. Their use makes it possible to abandon the creation of a new communication channel transmitting information, regardless of wired or wireless.

Special features of multiplexers

Some points affect the structure of multiplexers:

1. The number of components that are available.
2. What technology was used to create the multiplexer.
3. Configuration of the multiplexer. This factor depends on what tasks will be assigned to the multiplexer.

Modular multiplexers are very popular. These are modern instrument designs with a number of replaceable modules. With the help of such plug-in modules, it is possible to change the configuration of the multiplexer in accordance with the user's requirements and conditions of use.

The operation of the multiplexer is in many ways similar to the operation of switches, which provide the ability to connect multiple inputs and outputs. Such network equipment is powered by two types of input. One permissive and one control input.

On the video: The principle of operation of the multiplexer.

Types of multiplexers

A multiplexer is a network specific device. It has several simple and control inputs and one output. The presence of a certain number of such inputs is determined by the existing user requirements. Usually the number of inputs is limited to the maximum number - 16. How many inputs the multiplexer will have, as many channels for communication will be possible. Cascading tree technology is used to provide more inputs. This ensures the creation of the number of network communication channels required by the user on one network device.

Multiplexers can be of the following types:

Digital multiplexer. Such a device copies signals at the output. Signal copying does not use electrical impulse communication in and out.

Where multiplexers are used

Multiplexers are used in many areas of human life and work. Very often, multiplexers are used in telecommunication systems, video surveillance systems and in other areas. Almost all areas are very promising for the use of multiplexers.
The power industry uses multiplexers very widely. In this area, such devices facilitate the transmission of information data from various sensors that are located at a great distance from each other.

Information is transmitted using a single line. Communication networks often use multiplexers. They help reduce communication costs. That is why telecom operators often use it. The result of the multiplexer operation will be more noticeable, provided there is a long distance between the PBX.

The use of multiplexers for video conferencing is becoming quite popular. This implies two-way transmission, with subsequent processing, transformation and further presentation of interactive information data. All this takes place in real time and the signal is transmitted over a fairly long distance. When organizing video conferencing, its type is taken into account. The use of various special network devices depends on this type. Special group or individual videoconferencing terminals can be used.

An individual terminal is used when using a special mode of video communication in real time at his workplace. A laptop, personal computer, smartphone, tablet or a special terminal providing video communication can be used as an individual terminal. The group terminal is used for group video communication. For this, rooms are used in which special network devices are located. Such systems have only 1 common output and a certain number of inputs, which is necessary to create video communication. This can be provided by these network devices - multiplexers.
To create new local networks or expand the capabilities of existing ones, mult