H channel

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An H channel is a general transmission channel standardized by ITU-T in the early days of ISDN in recommendations I.231.6, I.231.7 and I.231.8 for circuit-switched transmission services for public telecommunications networks with a higher data transmission rate than the B channel . While the B channel offers 64 kbit / s as a data transmission rate, the H channel type should enable high bit-rate switched services with data transmission rates of 384 kbit / s (H0), 1,536 kbit / s (H11), 1,920 kbit / s (H12). H0 and H1 were backwards compatible with the PDH hierarchy of telecommunications networks in the Asia-Pacific and North American countries, respectively, and H12 with that in Europe. H-channels were intended for leased lines without D-channels , switched H-channels should have a built-in D-channel with 64 kbit / s. Switching centers for this type of channel were never developed due to a lack of demand, so that the switched H channel is only relevant on paper; it can still be found in old textbooks. The H-channel has also not caught on for leased lines; no NTPMs were built that offered an H-channel for connecting a terminal device . Instead, network terminations for leased lines with 2 Mbit / s that offer interfaces with variably adjustable bit rates are available on the market: usually from 50 bit / s to 2.048 Mbit / s. With these, the interface is usually designed according to the X.21 , X.30 , X.31 and V.35 standards commonly used in data communication , which in addition to the electrical and structural ( connector ) conditions also include bit rate adaptation and signaling between the network terminations on both sides of the dedicated line. Such network terminations are now also available for SDSL .

literature

  • Otfried Georg: Telecommunication technology. Manual for practice and teaching, 2nd edition, Springer Verlag Berlin Heidelberg, Berlin Heidelberg 2000, ISBN 978-3-642-63105-4 .
  • Peter Bocker: ISDN The service-integrated digital communication network. Second edition, Springer Verlag Berlin Heidelberg, Berlin Heidelberg 1987, ISBN 978-3-662-08033-7 .

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