Direct Inward Dialing

Direct Inward Dialing

Direct Inward Dialing (DID), also called Direct Dial-In (DDI) in Europe, is a feature offered by telephone companies for use with their customers' PBX systems, whereby the telephone company (telco) allocates a range of numbers all connected to their customer's PBX. As calls are presented to the PBX, the number that the caller dialed is also given, so the PBX can route the call to the desired person or bureau within the organization.

Developed by AT&T in the 1960s, patterned upon the earlier IKZ service of the Deutsche Bundespost, this feature enables companies to have fewer lines than extensions, while still having a unique number for each extension, callable from outside the company.

By way of example, each extension of the PBX system may be assigned a seven-digit external telephone number, with a fixed four- or five-digit prefix. Someone who knows the internal extension of his/her correspondent can dial the seven-digit number and be connected directly to the person called, bypassing the operator or PBX auto-attendant.

This system is also used by fax servers. Instead of an exchange at the end of the 234 000 line, a computer running fax server software and fax modem cards uses the last three digits to identify the recipient of the fax. This allows 1000 people to have their own individual fax numbers, even though there is only one 'fax machine'.

The corresponding trunk for outgoing calls from PBX to central exchange is called "Direct Dial Central Office" or DDCO.

DID (DDI) and VoIP aka "Call Through"

"DID" numbers have particular relevance for VoIP communications. In order for people connected to the traditional PSTN to call people connected to VoIP networks, DID numbers from the PSTN network are obtained by the administrators of the VoIP network, and assigned to a gateway in the VoIP network. The gateway will then route calls incoming from the PSTN across the IP network to the appropriate VoIP user. Similarly, calls originating in the VoIP network will appear to users on the PSTN as originating from one of the assigned DID numbers.

ellers

US DID numbers can be purchased in bulk from a Competitive Local Exchange Carrier. International DID numbers can be purchased in bulk from international DID providers. There are also a number of DID resellers offering DID numbers for individuals and small enterprises.

ee also

*Dialed Number Identification Service
*Dial plan


Wikimedia Foundation. 2010.

Игры ⚽ Поможем сделать НИР

Look at other dictionaries:

  • Direct inward dialing — (DID), also called direct dial in (DDI) in Europe and Oceania, is a feature offered by telephone companies for use with their customers private branch exchange (PBX) systems. In DID service the telephone company provides one or more trunk lines… …   Wikipedia

  • Direct Inward Dialing — Die Durchwahl aus einem Telefonnetz zu einem Teilnehmer ermöglicht den Anruf an einen Teilnehmer, der an einer privaten Telefonanlage angeschlossen ist. Zum Beispiel ist bei der Rufnummer 0291 1123 33 die 33 der mittels Durchwahl erreichbare… …   Deutsch Wikipedia

  • direct inward dialing — noun the ability to make an external telephone call to an internal extension within an organization …   Wiktionary

  • Direct Inward Dialing — telephone service in which a company receives a block of telephone numbers that can be accessed via a small number of actual telephone lines (enables private extensions without requiring extra lines …   English contemporary dictionary

  • direct-inward dialing —    (DID)    A PBX feature permitting outside calls to be dialed and connected directly to the stations …   IT glossary of terms, acronyms and abbreviations

  • Direct Inward Dialling — Die Durchwahl aus einem Telefonnetz zu einem Teilnehmer ermöglicht den Anruf an einen Teilnehmer, der an einer privaten Telefonanlage angeschlossen ist. Zum Beispiel ist bei der Rufnummer 0291 1123 33 die 33 der mittels Durchwahl erreichbare… …   Deutsch Wikipedia

  • Direct Dialling In — Die Durchwahl aus einem Telefonnetz zu einem Teilnehmer ermöglicht den Anruf an einen Teilnehmer, der an einer privaten Telefonanlage angeschlossen ist. Zum Beispiel ist bei der Rufnummer 0291 1123 33 die 33 der mittels Durchwahl erreichbare… …   Deutsch Wikipedia

  • Global Dialing Scheme — The Global Dialing Scheme (GDS) is numbering plan for H.323 networks. Based on the numerology provided by the United Nations International Telecommunications Union, GDS numerology resembles the international telephone system numbering plan, with… …   Wikipedia

  • DID — DID (Direct Inward Dialing)  возможность УАТС использовать несколько городских номеров для маршрутизации входящих вызовов из телефонной сети общего пользования (ТФОП). Разработанная в 1960 х годах компанией AT T и основанная на более… …   Википедия

  • Business telephone system — Early model 464G Western Electric key telephone set A business telephone system is any of a range of a multiline telephone systems typically used in business environments, encompassing systems ranging from small key systems to large scale private …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”