ISDN connection establishment
The establishment of a telephone connection within an ISDN takes the following steps:
- The calling user ( A subscriber ) usually causes his telephone A1 to send a SETUP message to the exchange by lifting the receiver .
- If a B-channel is free, it responds with a SETUP ACK message. The phone then generates the dial tone .
- The selected by the A subscriber number is sent each either one digit at a INFO message or as a block (in the so-called block choice) from the phone via the exchange towards target exchange.
- If a valid number has been dialed, the exchange sends a CALL PROCEEDING message to the telephone. This then does not allow any further dialing digits to be entered.
- The destination exchange sends a SETUP message to all of the terminals connected to the called user ( B subscriber ).
- Every terminal that has been programmed to accept calls for the specified destination number sends an ALERT message and begins to ring.
- The destination exchange sends the ALERT message back through the network to the A-subscriber's telephone. This then generates the ring tone .
- When the handset is lifted, the destination telephone B2 sends a CONNECT message to the destination exchange.
- The destination exchange forwards this message through the network and confirms it with a CONN ACK message to telephone B2 .
- It sends a REL message to all other terminals that are still ringing, which is confirmed by REL COM. The terminals then stop ringing.
- Telephone A1 confirms receipt of the CONNECT message with a CONN ACK message.
- The voice or data connection is established.
literature
- Otfried Georg: Telecommunication technology. A practical introduction. Springer Verlag, Berlin / Heidelberg 1996, ISBN 3-540-61381-1 .
- Hubert Zitt: ISDN & DSL for PC and telephone. Verlag Markt + Technik, Munich 2005, ISBN 3-8272-6987-3 .
- Peter Bocker: ISDN. Digital networks for voice, text, data, video and multimedia communication. 4th edition. Springer Verlag, Berlin / Heidelberg 1997, ISBN 3-642-64360-4 .
- Volker Jung, Hans-Jürgen Warnecke (Hrsg.): Handbook for telecommunications . Springer Verlag, Berlin / Heidelberg 1998, ISBN 3-642-97703-0 .
- Thomas Joos: PC networks. Verlag Markt + Technik, Munich 2008, ISBN 978-3-8272-4386-7 .
See also
Web links
- The ISDN D-Channel (accessed on July 20, 2017)
- Common interface for ISDN and IP (accessed on July 20, 2017)
- Digital connections on the public T-Net (accessed on July 20, 2017)
- Internet connection via analog telephone lines, ISDN and ADSL (accessed on July 20, 2017)