In telecommunication

Telecommunication

Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...

, a randomizer has the following meanings:

1. An algorithm that converts an input string into a seemingly random output string of the same length (e.g., by pseudo-randomly selecting bits to invert), thus avoiding long sequences of bits of the same value; in this context, a randomizer is also referred to as a scrambler
   Scrambler
   In telecommunications, a scrambler is a device that transposes or inverts signals or otherwise encodes a message at the transmitter to make the message unintelligible at a receiver not equipped with an appropriately set descrambling device...
   
   .
2. An analog or digital source of unpredictable (i.e., high entropy), unbiased, and usually independent (i.e., random) output bits. A "truly" random generator may be used to feed a (more practical) deterministic pseudo-random random number generator, which extends the random seed
   Random seed
   A random seed is a number used to initialize a pseudorandom number generator.The choice of a good random seed is crucial in the field of computer security...
   
    value.

Scrambling

Scramblers are primarily used for two reasons:

1. For energy dispersal on the carrier, reducing inter-carrier signal interference
   Interference (communication)
   In communications and electronics, especially in telecommunications, interference is anything which alters, modifies, or disrupts a signal as it travels along a channel between a source and a receiver. The term typically refers to the addition of unwanted signals to a useful signal...
   
   .
2. To enable accurate timing recovery on receiver equipment without resorting to redundant line coding.

Scramblers are essential components of physical layer

Physical layer

The physical layer or layer 1 is the first and lowest layer in the seven-layer OSI model of computer networking. The implementation of this layer is often termed PHY....

 system standards besides interleaved

Interleaving

In computer science and telecommunication, interleaving is a way to arrange data in a non-contiguous way to increase performance.It is typically used:* In error-correction coding, particularly within data transmission, disk storage, and computer memory....

 coding

Forward error correction

In telecommunication, information theory, and coding theory, forward error correction or channel coding is a technique used for controlling errors in data transmission over unreliable or noisy communication channels....

 and modulation

Modulation

In electronics and telecommunications, modulation is the process of varying one or more properties of a high-frequency periodic waveform, called the carrier signal, with a modulating signal which typically contains information to be transmitted...

. They are usually defined based on linear feedback shift register

Linear feedback shift register

A linear feedback shift register is a shift register whose input bit is a linear function of its previous state.The most commonly used linear function of single bits is XOR...

s (LFSRs) due to their good statistical properties and ease of implementation in hardware.

It is common for physical layer

Physical layer

The physical layer or layer 1 is the first and lowest layer in the seven-layer OSI model of computer networking. The implementation of this layer is often termed PHY....

 standards bodies to refer to lower-layer (physical layer

Physical layer

The physical layer or layer 1 is the first and lowest layer in the seven-layer OSI model of computer networking. The implementation of this layer is often termed PHY....

 and link layer

Link Layer

In computer networking, the link layer is the lowest layer in the Internet Protocol Suite , the networking architecture of the Internet . It is the group of methods or protocols that only operate on a host's link...

) encryption as scrambling as well. This may well be because (traditional) mechanisms employed are based on feedback shift registers as well.
Some standards for digital television

Digital television

Digital television is the transmission of audio and video by digital signals, in contrast to the analog signals used by analog TV...

, such as DVB-CA

Conditional access

Conditional Access is the protection of content by requiring certain criteria to be met before granting access to this content...

 and MPE

Multiprotocol Encapsulation

Multiprotocol Encapsulation, or MPE for short, is a Data link layer protocol definedby DVB which has been published as part of ETSI EN 301 192...

, refer to encryption at the link layer

Link Layer

In computer networking, the link layer is the lowest layer in the Internet Protocol Suite , the networking architecture of the Internet . It is the group of methods or protocols that only operate on a host's link...

 as scrambling

Scrambling

Scrambling is a method of ascending rocky faces and ridges. It is an ambiguous term that lies somewhere between hillwalking and rock climbing. It is often distinguished from hillwalking by defining a scramble as a route where hands must be used in the ascent...

.