AES3 is a standard for the exchange of digital audio signals between professional audio devices. AES3 was jointly developed by the Audio Engineering Society and the European Broadcasting Union, an AES3 signal can carry two channels of PCM audio over several transmission media including balanced lines, unbalanced lines, and optical fiber. It was published in 1985 and has been revised in 1992 and 2003, AES3 has been incorporated into the International Electrotechnical Commissions standard IEC60958, and is available in a consumer-grade variant known as S/PDIF. Early on, the standard was known as AES/EBU. Both AES and EBU versions of the standard exist and these variants are commonly known as S/PDIF. The standard has been revised in 1992 and 2003 and is published in AES, worldwide, it is the most commonly used method for digitally interconnecting audio equipment. The AES3 standard parallels part 4 of the international standard IEC60958, of the physical interconnection types defined by IEC60958, three are in common use. Type I connections use balanced, 3-conductor, 110-ohm twisted pair cabling with XLR connectors, Type I connections are most often used in professional installations and are considered the AES3 standard connector. The hardware interface is implemented using RS-422 line drivers and receivers. Type II connections use unbalanced, 2-conductor, 75-ohm coaxial cable with RCA connectors, Type II connections are used in most often in consumer audio installations and are often called coaxial S/PDIF connections. Type III Optical connections use optical fiber—usually plastic, but occasionally glass—with F05 connectors, like Type II, Type III Optical connections are also used in consumer audio installations and are often called optical S/PDIF connections. The AES-3id standard defines a 75-ohm BNC electrical variant of AES3 and this uses the same cabling, patching and infrastructure as analogue or digital video, and is thus common in the broadcast industry. AES3 digital audio format can also be carried over an Asynchronous Transfer Mode network, the standard for packing AES3 frames into ATM cells is AES47. For information on the synchronization of digital audio structures, see the AES11 standard, the ability to insert unique identifiers into an AES3 bit stream is covered by the AES52 standard. The precursor of the IEC60958 Type II specification was the Sony/Philips Digital Interface, the low-level protocol for data transmission in AES3 and S/PDIF is largely identical, and the following discussion applies for S/PDIF, except as noted. AES3 was designed primarily to support stereo PCM encoded audio in either DAT format at 48 kHz or CD format at 44.1 kHz. No attempt was made to use a carrier able to support both rates, instead, AES3 allows the data to be run at any rate, and encoding the clock, the basic unit of transmission is the frame. Frames contain 64 time slots and are produced once per sample time, at the highest level, each 192 consecutive frames are grouped into an audio block
XLR connectors, used for IEC 60958 Type I connections.
RCA connectors, used for IEC 60958 Type II connections.
F05/TOSLINK connector, used for IEC 60958 Type III connections.