Digital multiplexer is a combined logical device designed for controlled transmission of information from several data sources to the output channel. In fact, this device is a few digital position switches. It turns out that the digital multiplexer is a switch of input signals into one output line.
This device has three groups of inputs:
- addressable, the binary code on which determines which information input must be connected to the output;
- informational;
- allowing (strobe).
In the manufactured integrated circuits, the digital multiplexer has a maximum of 16 information inputs. If the device being designed requires a larger number, then the structure of the so-called multiplexer tree is built from several chips.
The digital multiplexer can be used to synthesize almost anylogical device, thereby significantly reducing the number of logic elements used in circuits.
Rules for the synthesis of devices based on multiplexers:
- Carnot map is built for the output function (based on the values of variable functions);
- select the order of use in the multiplexer circuit;
- a masking matrix is built, which must match the order of the multiplexer used;
- it is necessary to impose the resulting matrix on the Karnot map;
- after that, 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 let's move from theory to practice. Consider where such devices are used.
Flexible multiplexers are designed to generate digital streams (primary) at a speed of 2048 kbps from analog signals (voice), as well as data from digital interfaces for cross-switching of electronic channels at a speed of 64 kbps, transmission of a digital stream over an IP network /Ethernet and for converting line signaling and physical interfaces.
Using such a device, you can switch up to 60 (in some models this figure may be more) analog terminations in 1 or 2 E1 streams or 128 subscriber sets for four E1 streams. Usually, PM lines with in-band signaling act as analog terminations, or the signaling is implemented on a separate channel. Voice channel data can be compressed up to 32 kbps or 16 kbps perchannel, ADPCM encoding is used for this.
Flexible multiplexers allow you to use broadcast connections, that is, to feed signals from one of the digital or analog channels to several others. Often used to feed broadcast programs simultaneously to several different locations.
Optical multiplexers are devices designed to work with data streams using light beams that differ in amplitude or phase diffraction grating, as well as wavelength. The advantages of such devices include resistance to external influences, technical security, protection against hacking of transmitted information.
