Direct distance dialingwikipedia
Direct distance dialing (DDD) is a telecommunication service feature in which a caller may, without operator assistance, call any other user outside the local calling area.
direct distance dialingdirect dialdirect distance dialdirect distance diallingdirect-dialdialIDDD

North American Numbering Plan

Area codeArea codes<span style="white-space:nowrap;">Area code(s)
DDD was the term used when the North American Numbering Plan was implemented in the 1950s.
Direct distance dialing (DDD) was subsequently introduced across the country and by the early 1960s most areas of the Bell System had been converted and it was commonplace in cities and most larger towns.

Long-distance calling

long distancelong-distancelong-distance calling
On November 10, 1951, Englewood Mayor M. Leslie Denning made the first customer-dialed long distance call, to Mayor Frank Osborne of Alameda, California.
Before direct distance dialing (DDD), all long distance calls were established by special switchboard operators (long distance operators) even in exchanges where calls within the local exchange were dialed directly.

Telephone exchange names

telephone exchange namescentral office nametelephone exchange
Customers of the ENglewood 3, ENglewood 4 and TEaneck 7 exchanges, who could already dial New York City and area, were able to dial 11 cities across the United States, simply by dialing the three-digit area code and the seven-digit number, which at the time consisted of the first two letters of the central office name and five digits.
Eventually, starting in the late 1940s, all local numbering plans were changed to the 2L-5N system to prepare for nationwide Direct Distance Dialing.

Englewood, New Jersey

EnglewoodEnglewood, New JerseyEnglewood, NJ
The first direct-dialed long-distance telephone calls were possible in the New Jersey communities of Englewood and Teaneck.
Direct distance dialing, which allowed callers to reach other users outside their local calling area without operator assistance, was introduced to the public in Englewood.

Subscriber trunk dialling

STDsubscriber trunk diallingSTD code
In the United Kingdom and other parts of the Commonwealth of Nations, the equivalent terms are or were "STD", for subscriber trunk dialing, and "ISD" for international subscriber trunk dialing.
The corresponding term in the North American Numbering Plan, e.g. in the United States and Canada, is direct distance dialing.

Area codes 415 and 628

415/628415area code 415
For a short time in the early 1950s, area code 318 was temporarily used, initially by customers in Englewood, New Jersey, participating in the first customer direct distance dialing experiment to reach San Francisco as well as some areas north of the Golden Gate.

Automatic message accounting

automatic message accountingmessage registerscall accounting
As this and other improved technologies became available, as well as Automatic Message Accounting (AMA) computers to process the long distance records into customer bills, the reach of DDD was slow in the 1950s, but quickened in the early 1960s.
When direct distance dialing (DDD) was introduced in the US, message registers no longer sufficed for dialed telephone calls.

M. Leslie Denning

On November 10, 1951, Englewood Mayor M. Leslie Denning made the first customer-dialed long distance call, to Mayor Frank Osborne of Alameda, California.
On November 11, 1951, Denning became the first to use the direct distance dialing telephone facility in 1951 to contact Mayor Frank Osborne of Alameda, California.

Frank Osborne (California politician)

Frank Osborne
On November 10, 1951, Englewood Mayor M. Leslie Denning made the first customer-dialed long distance call, to Mayor Frank Osborne of Alameda, California.
He was the recipient of the first phone call to use the direct distance dialing telephone facility in 1951 dialed by Mayor M. Leslie Denning of Englewood, New Jersey.

Number pooling

number pooling
Call routing can now be done based on the area code, central office code and even the first two digits of the line number, although routing based on digits past the central office code is usually limited to cases of competitive local exchange carriers, number pooling and number portability.
The North American Numbering Plan is based on fixed-length telephone numbers; when area codes (1947) and direct distance dialling (1951) were first introduced, North American numbers were gradually extended to a fixed length in the format 1 + three-digit area code + three-digit exchange prefix + four-digit subscriber number.

Operator assistance

operator assistanceoperator-assistedperson-to-person
Direct distance dialing (DDD) is a telecommunication service feature in which a caller may, without operator assistance, call any other user outside the local calling area.
Operator-assisted calls can be more expensive than direct dial calls.

Signaling System No. 5

SS5Signaling System No. 5Signaling System 5, (SS5)
The international trunks used Signaling System No. 5, a "North Atlantic" version of the North American multi-frequency signaling system, with minor modifications including slightly higher digit rate.
The Signaling System No. 5 (SS5) is a multi-frequency (MF) telephone signaling system that was in use from the 1970s for International Direct Distance Dialing (IDDD).

Panel switch

panel switchpanelPanel system
With semiautomatic operation analogous to the early days of the panel switch, the operator in the originating city used a multifrequency keypad to dial an access code to connect to the correct city and to send the seven digit number to incoming equipment at the terminating city.
The introduction of direct distance dialing (DDD) in the 1950s required the addition of automatic number identification equipment for centralized automatic message accounting.

Number One Crossbar Switching System

1XBNo. 1 Crossbar1XB switch
Common control switches such as 1XB switch were fairly quickly retrofitted to provide ANI, and most 5XB switches were initially installed with ANI services.
It called in an auxiliary sender when necessary to implement Direct Distance Dialing (DDD).

Multi-frequency signaling

multi-frequencyMFmultifrequency
With semiautomatic operation analogous to the early days of the panel switch, the operator in the originating city used a multifrequency keypad to dial an access code to connect to the correct city and to send the seven digit number to incoming equipment at the terminating city.
* "Speeding Speech", a 1950s Bell System film, depicts a 2-1-1 long distance operator manually entering a number on an MF keypad just prior to the introduction of direct distance dialing.

Number Five Crossbar Switching System

5XB switchNo. 5 Crossbar switch5XB
Common control switches such as 1XB switch were fairly quickly retrofitted to provide ANI, and most 5XB switches were initially installed with ANI services.
This test facility became more valuable as Centrex, direct distance dialing, and other innovations brought more complications to the tasks of translation and trunk selection.

List of original NANP area codes

original area codesoriginal 86 area codesoriginal numbering plan areas
In preparation for direct distance dialing, AT&T and the Bell System developed the North American Numbering Plan in the 1940s.

PSTN network topology

In the United States and Canada, the Bell System network topology was the switching system hierarchy implemented and operated from the late 1940s to the 1980s for the purpose of integrating the diverse array of local telephone companies and telephone numbering plans to achieve nationwide Direct Distance Dialing (DDD) by telephone subscribers.

Area codes 418 and 581

418 and 581418418, 581
However, in the 1970s, as direct distance dialling was introduced to the far northern and western portions of 418, these points were shifted to area code 819, leaving the present area.

Switchboard operator

telephone operatorswitchboard operatoroperator
Before the advent of operator distance dialing and customer Direct Dial (DDD) calling, switchboard operators would work with their counterparts in the distant central office to complete long distance calls.

Telephone numbers in Brazil

+55Area codeBrazil
Even shorter numbers used to exist in previous decades, especially in small towns and before direct distance dialing became universal.

Via Net Loss

Via Net Loss (VNL) is a network architecture of telephone systems using circuit switching technologies deployed in the 1950s with Direct Distance Dialing and used until the late 1980s.

Area codes 416, 647, and 437

416416, 647416, 647, 437
They were lengthened to seven (2L+5N) in the 1950s to accommodate direct distance dialling.

Push-button telephone

push-button telephonepush-button dialingpushbutton telephones
The 1951 introduction of direct distance dialing required automatic transmission of dialed numbers between distant exchanges, leading to use of inband multi-frequency signaling within the Long Lines network while individual local subscribers continued to dial using standard pulses.