POTS codec
Encyclopedia
A POTS codec is a device
used in broadcast engineering
to send high-fidelity digital audio
over regular telephone line
s. A hardware
codec
, implemented with digital signal processing
, is used to compress the audio data enough to travel at a bitrate
equivalent to a 33.6k modem. Thus, it is a modem able to use plain old telephone service
(POTS) to send monophonic
(and now stereophonic) audio.
An alternate version of the technology
is the ISDN codec, which instead uses ISDN lines, and can use channel bonding
to achieve higher quality audio.
ing by radio stations.
ISDN has the advantage of being natively digital
, and a full 64 or 128kb
/s
when using both channels, which results in fewer compression and potential compression artifact
s. However, special lines must be run to a location, and must be ordered well in advance of the event so that there is plenty of time for installation. Because of this, ISDN codecs are generally only useful for recurring events such as weekly nightclub
s, or major events which warrant the expense
. ISDN is also no longer being installed in some areas, being supplanted by DSL, which does not guarantee quality of service
though a virtual circuit
as ISDN does.
Since POTS lines are almost universally available, the POTS codec can be set up nearly anywhere with little or no notice.
Digital codecs are far superior to the old telephone hybrid
s and frequency extender
s previously used to send analog audio over one or more lines. Telephone codecs also eliminate the need for remote pickup unit
s, a wireless
method of remote broadcasting. RPUs are still used in situations where no telephone line is available.
and portable
for the remote. Audio can be sent in either direction, and most can also pass low-speed non-audio data, allowing the remote DJ to control broadcast automation
or other studio equipment via RS-232
. Many have an automatic redial if the line should become disconnected. The remote unit usually has some basic mixer
functions, while the studio unit usually has some kind of digital output.
Some codecs can use both ISDN and POTS, implementing codecs like G.722
, MPEG AAC
, aacPlus, Apt-X
and AAC-LD
(low-delay
). Some can even use GSM, and some have variable bitrate
to compensate
for poor connections. It is also possible to bond two POTS lines together for redundancy
and fault tolerance, and better bandwidth
. A MPEG-1 Layer II codec even supports audio over IP
.
Codecs are also made by Comrex, Sonifex, Tieline
, APT and Telos
among others.
Information appliance
In general terms, an information appliance or information device is any machine or device that is usable for the purposes of computing, telecommunicating, reproducing, and presenting encoded information in myriad forms and applications....
used in broadcast engineering
Broadcast engineering
Broadcast engineering is the field of electrical engineering, and now to some extent computer engineering and information technology, which deals with radio and television broadcasting...
to send high-fidelity digital audio
Digital audio
Digital audio is sound reproduction using pulse-code modulation and digital signals. Digital audio systems include analog-to-digital conversion , digital-to-analog conversion , digital storage, processing and transmission components...
over regular telephone line
Telephone line
A telephone line or telephone circuit is a single-user circuit on a telephone communication system...
s. A hardware
Computer hardware
Personal computer hardware are component devices which are typically installed into or peripheral to a computer case to create a personal computer upon which system software is installed including a firmware interface such as a BIOS and an operating system which supports application software that...
codec
Codec
A codec is a device or computer program capable of encoding or decoding a digital data stream or signal. The word codec is a portmanteau of "compressor-decompressor" or, more commonly, "coder-decoder"...
, implemented with digital signal processing
Digital signal processing
Digital signal processing is concerned with the representation of discrete time signals by a sequence of numbers or symbols and the processing of these signals. Digital signal processing and analog signal processing are subfields of signal processing...
, is used to compress the audio data enough to travel at a bitrate
Bitrate
In telecommunications and computing, bit rate is the number of bits that are conveyed or processed per unit of time....
equivalent to a 33.6k modem. Thus, it is a modem able to use plain old telephone service
Plain old telephone service
Plain old telephone service is the voice-grade telephone service that remains the basic form of residential and small business service connection to the telephone network in many parts of the world....
(POTS) to send monophonic
Monaural
Monaural or monophonic sound reproduction is single-channel. Typically there is only one microphone, one loudspeaker, or channels are fed from a common signal path...
(and now stereophonic) audio.
An alternate version of the technology
Technology
Technology is the making, usage, and knowledge of tools, machines, techniques, crafts, systems or methods of organization in order to solve a problem or perform a specific function. It can also refer to the collection of such tools, machinery, and procedures. The word technology comes ;...
is the ISDN codec, which instead uses ISDN lines, and can use channel bonding
Channel bonding
Channel bonding is a computer networking arrangement in which two or more network interfaces on a host computer are combined for redundancy or increased throughput....
to achieve higher quality audio.
Uses
The main use of a POTS or ISDN codec is for remote broadcastRemote broadcast
In broadcast engineering, a remote broadcast is broadcasting done from a location away from a formal television studio and is considered an electronic field production . A remote pickup unit is usually used to transmit the audio and/or video back to the television station, where it joins the...
ing by radio stations.
ISDN has the advantage of being natively digital
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
, and a full 64 or 128kb
Kilobit
The kilobit is a multiple of the unit bit for digital information or computer storage. The prefix kilo is defined in the International System of Units as a multiplier of 103 , and therefore,...
/s
Second
The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock....
when using both channels, which results in fewer compression and potential compression artifact
Compression artifact
A compression artifact is a noticeable distortion of media caused by the application of lossy data compression....
s. However, special lines must be run to a location, and must be ordered well in advance of the event so that there is plenty of time for installation. Because of this, ISDN codecs are generally only useful for recurring events such as weekly nightclub
Nightclub
A nightclub is an entertainment venue which usually operates late into the night...
s, or major events which warrant the expense
Expense
In common usage, an expense or expenditure is an outflow of money to another person or group to pay for an item or service, or for a category of costs. For a tenant, rent is an expense. For students or parents, tuition is an expense. Buying food, clothing, furniture or an automobile is often...
. ISDN is also no longer being installed in some areas, being supplanted by DSL, which does not guarantee quality of service
Quality of service
The quality of service refers to several related aspects of telephony and computer networks that allow the transport of traffic with special requirements...
though a virtual circuit
Virtual circuit
In telecommunications and computer networks, a virtual circuit , synonymous with virtual connection and virtual channel, is a connection oriented communication service that is delivered by means of packet mode communication...
as ISDN does.
Since POTS lines are almost universally available, the POTS codec can be set up nearly anywhere with little or no notice.
Digital codecs are far superior to the old telephone hybrid
Telephone hybrid
Telephone hybrids are an essential functional component of the Public Switched Telephone Network . The term also describes the piece of equipment used in broadcast facilities to enable the airing of telephone callers....
s and frequency extender
Frequency extender
In broadcast engineering, a frequency extender is an electronic device that allows high-fidelity analogue audio to be sent over regular POTS telephone lines, without the loss of higher audio frequencies . It is an extended concept of a telephone hybrid.The concept uses frequency shifting, in order...
s previously used to send analog audio over one or more lines. Telephone codecs also eliminate the need for remote pickup unit
Remote pickup unit
A remote pickup unit or RPU is a radio system using special radio frequencies set aside for electronic news gathering and remote broadcasting. It can also be used for other types of point-to-point radio links....
s, a wireless
Wireless
Wireless telecommunications is the transfer of information between two or more points that are not physically connected. Distances can be short, such as a few meters for television remote control, or as far as thousands or even millions of kilometers for deep-space radio communications...
method of remote broadcasting. RPUs are still used in situations where no telephone line is available.
Functions
Both kinds of codec usually come in two types of units: rackmount for the studioStudio
A studio is an artist's or worker's workroom, or the catchall term for an artist and his or her employees who work within that studio. This can be for the purpose of architecture, painting, pottery , sculpture, scrapbooking, photography, graphic design, filmmaking, animation, radio or television...
and portable
Portable
Portable may refer to:* Portable building, a manufactured structure that is built off site and moved in upon completion of site and utility work...
for the remote. Audio can be sent in either direction, and most can also pass low-speed non-audio data, allowing the remote DJ to control broadcast automation
Broadcast automation
Broadcast automation incorporates the use of broadcast programming technology to automate broadcasting operations. Used either at a broadcast network, radio station or a television station, it can run a facility in the absence of a human operator...
or other studio equipment via RS-232
RS-232
In telecommunications, RS-232 is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between a DTE and a DCE . It is commonly used in computer serial ports...
. Many have an automatic redial if the line should become disconnected. The remote unit usually has some basic mixer
Mixing console
In professional audio, a mixing console, or audio mixer, also called a sound board, mixing desk, or mixer is an electronic device for combining , routing, and changing the level, timbre and/or dynamics of audio signals. A mixer can mix analog or digital signals, depending on the type of mixer...
functions, while the studio unit usually has some kind of digital output.
Some codecs can use both ISDN and POTS, implementing codecs like G.722
G.722
G.722 is a ITU-T standard 7 kHz wideband speech codec operating at 48, 56 and 64 kbit/s. It was approved by ITU-T in November 1988. Technology of the codec is based on sub-band ADPCM ....
, MPEG AAC
Advanced Audio Coding
Advanced Audio Coding is a standardized, lossy compression and encoding scheme for digital audio. Designed to be the successor of the MP3 format, AAC generally achieves better sound quality than MP3 at similar bit rates....
, aacPlus, Apt-X
Apt-X
The digital audio data reduction technology now known as apt-X is a family of proprietary audio codec compression algorithms developed by APT Licensing. From March 14, 2009, APT Licensing changed the company's trading identity to APTX. The original algorithm was developed in the 1980s by Dr...
and AAC-LD
AAC-LD
The MPEG-4 Low Delay Audio Coder is audio compression format designed to combine the advantages of perceptual audio coding with the low delay necessary for two-way communication. It is closely derived from the MPEG-2 Advanced Audio Coding format...
(low-delay
Lag
Lag is a common word meaning to fail to keep up or to fall behind. In real-time applications, the term is used when the application fails to respond in a timely fashion to inputs...
). Some can even use GSM, and some have variable bitrate
Variable bitrate
Variable bitrate is a term used in telecommunications and computing that relates to the bitrate used in sound or video encoding. As opposed to constant bitrate , VBR files vary the amount of output data per time segment...
to compensate
Compensation (engineering)
In engineering, compensation is planning for side effects or other unintended issues in a design. The design of an invention can itself also be to compensate for some other existing issue or exception....
for poor connections. It is also possible to bond two POTS lines together for redundancy
Redundancy (information theory)
Redundancy in information theory is the number of bits used to transmit a message minus the number of bits of actual information in the message. Informally, it is the amount of wasted "space" used to transmit certain data...
and fault tolerance, and better bandwidth
Bandwidth (computing)
In computer networking and computer science, bandwidth, network bandwidth, data bandwidth, or digital bandwidth is a measure of available or consumed data communication resources expressed in bits/second or multiples of it .Note that in textbooks on wireless communications, modem data transmission,...
. A MPEG-1 Layer II codec even supports audio over IP
Audio over IP
Streaming audio over IP networks is being increasingly used by broadcasting companies, among others, to provide high-quality audio feeds over distance across an IP network such as the Internet. The application is also known as audio contribution over IP in reference to the programming...
.
Codecs are also made by Comrex, Sonifex, Tieline
Tieline
Tieline Technology has offices in Indianapolis in the USA and in Perth, Western Australia . The company has a wide and established distribution network throughout Europe, the Americas and Australasia. Tieline develops a range of broadcast audio codecs that are sold to television and radio networks...
, APT and Telos
Telos Systems
Telos Systems is an American corporation manufacturing audio products primarily for broadcast stations. Headquartered in Cleveland, Ohio, USA, Telos develops, sells, and supports equipment such as telephone hybrids and on-air talkshow systems, ISDN codecs, POTS codecs, IP codecs, and audio logging...
among others.