External connection
External connection or special connection is the name given to the connection of a subscriber connection to a different local network exchange (analog or DIVO ) than the geographically intended connection area . The subscriber connection has a call number from the connection area to which it is connected via switching.
At the time of the introduction of ISDN there were more and more external connections in order to bypass switching centers that had not yet been digitized and still be able to provide ISDN to all customers. If the line was longer than 8 km, regenerators were used to pick up the signal and send it out again. These worked on OSI layer 1 . Since the ISDN signal is digital, no loss of quality is possible as long as the route has been correctly measured and planned.
In the case of DSL , there were also third-party connections because not all connection areas had their own DSLAM .
In the emergency call system 73 there were also external connections of emergency call connections if the connection area was not equipped with an emergency call station.
Individual evidence
- ↑ T-Com service description Additional services T-ISDN multi-device connection point 23 as of August 1, 2005
- ^ ISDN - The new telecommunications network of the Deutsche Bundespost Telekom, R. v. Decker's Taschenbuch Telekommunikation, 4th revised and expanded edition, 1992, p. 17