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Directory assistance systems incorporate a wide range of automation to reduce the cost of human operators. Almost all systems use custom database software to locate listings quickly.
Most directory assistance systems use automated readback systems to give out the phone number. This frees the directory assistance operator to move on to another caller as soon as the correct listing is located.
Some systems have "store and forward" technology which records "city and state" the caller is requesting and then plays the city and state speech to the operator before they come online and then say "Residential or business listing?" or simply "What listing please?"
Interactive voice response systems have been added to many directory assistance systems. These complex systems use speech recognition and recorded speech or speech synthesis to handle the entire call without live operator intervention.
Most systems recognize location and listing. If recognition confidence is high, the best result is played to the caller. If confidence is low, the caller's request is played back to a live operator, who locates the correct listing.
Directory assistance data sources
The services of 4-1-1 queries is often outsourced to a call centre who specializes in that function. Historically, when a single carrier provided most of the telephony services for a region, the data used to satisfy the search could exclusively come for that carriers subscriber rolls. Today, when the market is fragmented amongst many carriers, the data must be aggregated by a data aggregator specializing in directory listings, such as LSSi. The data aggregator distributes the data to the 4-1-1 services either on a "live" basis, actually servicing each query, or by periodically transferring large swaths of listings to the call center's systems for local searching.
The data aggregator collects the data from the rolls of many telecommunication carriers. Some carriers such as Vonage do not send their customer rolls to the aggregator. Their customers can get their listings in the directory assistance database using a free service such as ListYourself.net.
In the North American Numbering Plan (covering Canada and the United States), directory assistance may be contacted by dialing 4-1-1 (one of the N11 codes) or to get a listing in a remote or non-local area code, directory assistance is available at 1-area code-555-1212.
However, a 411 landline call will provide local listings as well as nationwide listings and sometimes international listings.
Most telephone companies permit up to two listings per 411 call. All wireless carriers offer nationwide listings with 411, and some offer additional Enhanced Directory Assistance services.
U.S. wireline telephone companies classify DA into four rate classes.
- 411 LDA — Local Directory Assistance. 411 is dialled and the operator is requested to search for a listing in a group of area codes "LATA" local to the caller. Example: the caller lives in area code 630 (Oak Brook, IL) and request a listing for a business in area code 312 (Chicago, IL). In this case, AT&T Illinois bills the call at $1.25 plus taxes.
- 411 NDA — National Directory Assistance. 411 is dialled and the operator is requested to search for a listing in an area code not local to the caller. Example: The caller lives in area code 630 (Oak Brook, IL) and requests a listing for a business in area code 213 (Los Angeles, CA). In this case AT&T Illinois bills the call at $1.99 plus taxes.
- 411 (area code) 555-1212 — National Directory Assistance. This example assumes the caller is in Oak Brook, IL (area code 630) and uses MCI as their long distance carrier. Example: The caller is looking for a listing in Los Angeles, CA (area code 213) and dials 213-555-1212. In this case MCI bills the call at $3.49 plus taxes.
- AT&T International Directory Assistance calls are $7.95 plus taxes. Dial 00 and ask for the international directory assistance operator. See www.consumer.att.com/global/english/country_codes.html for additional information and country and city codes.
Toll-free directory assistance
In the U.S., directory assistance for companies with toll-free "800 numbers" (with area codes 800, 888, 877, 866, 855) is available from toll-free directory assistance.
Toll-free directory assistance is provided by AT&T as mandated by the Federal Communications Commission. Companies must request to have their toll-free number listed and pay AT&T each time their phone number is released to a Toll-free directory assistance caller. AT&T had applied for discontinuing this service but it remains active.
Companies specializing in free directory assistance
Recently private companies have entered the directory assistance market by offering free directory assistance. Customers often must listen to an advertisement prior to receiving directory services.
In the United Kingdom, directory assistance is called directory enquiries. The service is provided by a variety of different companies, with a variety of call charges, each company reached by dialling a six digit number beginning 118. These companies supply information from the Operator Services Information System (OSIS), which is run by Directory Solutions, a division of BT Wholesale. OSIS accepts updates from telecoms providers seven days a week, and supplies that information to the enquiry companies six days a week. There are currently over 200 providers. Three of these, 118 500 (BT), 118 888 (Conduit) and 118 118 (The Number), have over 90% of the market, mostly due to heavy advertising.
Directory enquiries used to be reached by dialling 192 (domestic numbers) or 153 (foreign), with the service supplied by the telephone company providing the fixed or mobile service to the calling telephone. These numbers were switched off on 24 August 2003 following the introduction of competition to directory enquiries.
A number offering a directory enquiries service allowing people to request to be put through to a mobile phone number was established in June 2009. 118 800 proved to be controversial, however, when it was revealed that it was making available 15 million mobile numbers that it had bought from market researchers. Its website has been temporarily suspended to deal with technical issues and improve the service. The site was suspended within weeks of its launch so that the company could rengineer the site to enable the large number of ex-directory requests to be handled more efficiently. Viral emails regarding 118800 are generally thought to be responsible for the deluge of unsubscribe requests. The virals spread panic by alleging that the 118800 service was about to give out phone numbers which would be available to marketers. The 118800 service have maintained that these emails are without substance referring enquirers to their website where the service is explained. 118800 do not, at any time, release telephone numbers to callers but rather send a message to the mobile phone owner letting them know that the enquirer wishes to be connected to them. The recipient of the call retains the right to accept or refuse the call but either way the caller is never notified of the mobile phone number being contacted.
In mainland China, (area code) 114 is dialed for directory assistance in that area code. This call is charged at the same rate as a regular call. 
- *AT&T Inc. (16 November 1999). "Discontinuance - AT&T Toll-Free Directory Assistance Service - 1-800-555-1212". FCC Public Notices. Federal Communications Commission. Retrieved 2007-12-28.
- Bernstein, Fred A. (9 March 2006). "The 411 on Directory Assistance". The New York Times. Retrieved 1 May 2010.
- "BT Wholesale Directory Solutions - About Us". British Telecom. Retrieved 13 January 2010.
- "118 800 To Connect UK To Millions Of Mobile Numbers". Real Wire. 9 June 2009. Retrieved 19 July 2009.
- Osborne, Hilary (13 July 2009). "Mobile phone directory suspended". London: The Guardian. Retrieved 14 July 2009.
- "118800 Mobile Enquiry Service Temporarily Suspended'". PR Log. 29 July 2009.
- "The Only Directory with Millions of Mobile Numbers". 118800.co.uk. 15 June 2009. Retrieved 15 July 2009.
- "号码百事通". China Telecom. Retrieved 14 July 2013.
- Mark Lawson, The Guardian, 19 March 2005, "Dial 0 for progress"
- Patrick Hosking, New Statesman, 6 September 2004, "The business - Patrick Hosking wonders if 999 will be privatised"