Extension
An extension or Austrian flap enables an extension of a telephone system to be reached directly via public telephone networks instead of being switched at the answering station . The extension forms the end of a phone number .
English terms for extension are direct dial in ( DDI ) and direct inward dial ( DID ).
The assignment of extensions to extensions is done by programming the telephone system accordingly. In German-speaking countries, the extension 0 is usually used for the inquiry station. If you can assign multiple-digit extensions, with each single-digit extension you do without all multi-digit extensions that begin with the respective digit.
In Germany, each system connection is assigned a basic number (e.g. 1234) and a number block with at least ten one to five-digit extensions (e.g. 0 to 29). Written extensions are often separated from the rest of the phone number with a hyphen, following DIN 5008 . The extension number is clearly visible in this notation, for example extension 14 for the number 1234-14 . This notation is not used internationally. According to Recommendation E.123 of the International Telecommunications Union , no symbols should be used to highlight extensions.
In Austria , an extension in the telephone exchange is also known as a flap . The term comes from the optical signaling on a flap cabinet . In contrast to Germany, no number blocks are assigned, the number and length of the extensions are up to the end customer, who can use it to flexibly design his number plan. Only the E.164 guideline limits the total length of the phone number including the area code (without the traffic code 0) and extension to 13 digits. For a primary rate connection a shortened number (by 2 digits) is usually assigned, so that more extensions are possible.
In the Czech Republic , all extensions with direct dialing in a telephone system have the same number length. The mediation is achieved by choosing the appropriate number of ones. For example: if four-digit extension numbers are used in a telephone system, the operator will have the number 1111.
literature
- Werner Bärwald: Expert practice lexicon communication technologies. Expert Verlag, ISBN 978-3-8169-2843-0 .
Individual evidence
- ↑ Direct Dial In (DDI) with ISDN30 / 30e . BT Group . Retrieved October 24, 2012.
- ↑ Understanding Direct-Inward-Dial (DID) on IOS Voice Digital (T1 / E1) interfaces . Cisco Systems . Retrieved October 24, 2012.