Direct Inward Dialing
Direct Inward Dialing (DID, also called DDI in Europe) is a feature offered by telephone companies for use with their customers' PBX system, 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 dialled is also given, so that the PBX can decide which person in the office to route the call to.
Developed by AT&T, 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'.
When people give out their work number and say it's a "direct line", often what they mean is that it's a DID number.
When you buy a phone line from a VOIP phone service provider, offering phone service over broadband, the number that they provide to you, in technical terms is a DID number. This is the number that they have assigned to you to connect you to the old PSTN Networks around the world. Any service provider who wants to offer a phone service over ip address, needs to buy DID number from his CLEC or any other large service provider like Level 3 or IP Communications in the United States or go to a consortium to buy these numbers like DIDXchange or DIDX.org.
If you are using an IP PBX like Asterisk and you want to connect yourself to PSTN so people can call your office, you can either 1) buy an Analog or E1/T1 card from Digium, or 2) buy DID number from a service provider like virtualphoneline.com, broadvoice.com or voicepulse.com that will then come to your IPPBX as a real phone line and then you can use as your phone number, and route it to your ivr or direct extension. You can get a FREE UK DDI from IPStar.us or buy commercial DID's from service providers like Virtual Phone Line Service.
Globalization - Use of DID in VOIP Industry The DID's have become very popular in the new VOIP telephone service industry. Many service providers like ipstar.us give out the UK numbers for free to be used by any standard SIP based phone service like freeworlddlaip.com or phoneopia.com.
They same did number are used by Vonage, Broadvoice and Lingo etc. The Power of the internet now allows service providers to become Global Telephone carriers, rather then just local area service provider.
Hosted PBX providers such as ip-pabx.com use these same did numbers, to offer global phone lines, over there hosted pbx services.
List of telephony terms:
3gpp - a-law - abbreviated dialing - adsl - ani - answering machine - apn - automatic ring back - b-channel - baud - bell 202 modem - bit rate - bonding - bri - busy signal - cable modem - call-progress tones - call accounting - call capture - call forwarding - call originator - call park - call pick-up - call transfer - call waiting - call waiting deluxe - called party - caller id - caller id spoofing - calling party - carrier wave - cbr - ccitt - cdma - cdma2000 - cellular repeater - celp - channel - clec - clock rate - codec - collect call - conference - conference call - crc - csd - d-channel - data compression - device driver - dial-up - dial - dial tone - direct-inward-dialing - direct distance dialing - distinctive ring - dnis - dsl - dsp - dtmf - dtr - duplex - echo cancellation - edge - extension - fax - fcc - fdma - fidonet - follow-me - g.711 - g.723.1 - g.723 - g.726 - g.lite - gprs - gps - gsm - h.323 - harmonic - headphones - hscsd - hspda - iad - idsn - internet call waiting - isp - ivr - jack plug - local loop - long distance - microcontroller - mobile phone - modem - modulation - mu-law - music-on-hold - night service - off-hook - on-hook - pabx - pager - payphone - pbx - pcm - pots - prank call - precise tone plan - pstn - pulse dialling - push to talk - ring modulation - ring tone - ringback - ringing signal - rj11 - roaming - serial communications - serial port - signal noise - sim - simplex - sit - sms - softmodem - switchboard operator - tapi - tdma - telecommunications - telemarketing - telephone - telephone call - telephone card - telephone company - telephone exchange - telephone line - telephone number - telephone numbering plan - telephone operator - telephone switchboard - telephony - tts - twisted pair - umts - v.32 - v.32bis - v.34 - v.42bis - vbr - vertical service code - voicemail - voip - vox - wap - wav - wi-fi - wimax - wire
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