Digital multiplexer: description, purpose, types

A digital multiplexer is a logical combination device that is designed to manage the transfer of information from several data sources to an output channel. In fact, this device is a number of digital position switches. It turns out that the digital multiplexer is a switch of input signals to one output line.

This device has three groups of inputs:

• Address, binary code on which determines what information input must be connected to the output;
• Information;
• Resolving (stroking).

In the produced integrated circuits, the digital multiplexer has a maximum of 16 information inputs. If the projected device requires more, then the structure of the so-called multiplexer tree of several microcircuits is constructed.

A digital multiplexer can be used to synthesize almost any logical device, thereby significantly reducing the number of logic elements used in circuits.

Rules for synthesizing instruments based on multiplexers:

• A Carnot map is constructed for the output function (by the values of the variable functions);
• The order of use in the multiplexer circuit is selected;
• A masking matrix is constructed, which must correspond to the order of the multiplexer used;
• It is necessary to superimpose the resulting matrix on the Carnot map;
• After this, the function is minimized separately for each area of the matrix;
• Based on the results of minimization, it is necessary to construct a scheme.

Now, from theory to practice. Consider where these devices are used.

Flexible multiplexers are designed to generate digital streams (primary) at a speed of 2048 kbit / s from analog signals (speech), as well as data from digital interfaces for cross-connecting electronic channels at a speed of 64 kbit / s, digital stream transmission over the IP / Ethernet network and for conversion Linear signaling and physical joints.

With the help of such a device, up to 60 (in some models this number may be larger) can be connected to analogue endings in 1 or 2 E1 streams or 128 subscriber kits for four E1 streams. Typically, analogue ends are PM lines with in-band signaling, or signaling is implemented on a separate channel. The voice channel data can be compressed to 32 or 16 kbit / s per channel, using the ADPCM encoding.

Flexible multiplexers allow the use of broadcast connections, that is, to send signals from one of the digital or analog channels to several others. They are often used for the delivery of broadcasting programs simultaneously into several different points.

Optical multiplexers are devices designed to work with data streams with the help of light beams, which differ in amplitude or phase diffraction grating, as well as in wavelength. The advantages of such devices include resistance to external influences, technical security, protection against hacking of transmitted information.