1 Telephone numbers in the U.S. BASIC TELECOMMUNICATIONS

2 The telephone numbers for North America conform to the North American Numbering Plan (NANP) and consist of 10 digits The first three digits are the area code The next three digits are the CO code The remaining four digits are the station code The number 1 signals a long distance call For international calls three additional digits are used at the beginning of the sequence to specify the country code The telephone numbers for North America conform to the North American Numbering Plan (NANP) and consist of 10 digits The first three digits are the area code The next three digits are the CO code The remaining four digits are the station code The number 1 signals a long distance call For international calls three additional digits are used at the beginning of the sequence to specify the country code BASIC TELECOMMUNICATIONS

3 A telephone number is a sequence of digits used to call from one telephone line to another in a public switched telephone network. When telephone numbers were invented, they were short, as few as one, two or three digits — and were given orally to a switchboard operator. As phone systems have grown and interconnected to encompass the world, telephone numbers have become longer. A telephone number is a sequence of digits used to call from one telephone line to another in a public switched telephone network. When telephone numbers were invented, they were short, as few as one, two or three digits — and were given orally to a switchboard operator. As phone systems have grown and interconnected to encompass the world, telephone numbers have become longer. BASIC TELECOMMUNICATIONS

4 In addition to telephones, they now access other devices, such as modems and fax machines. The latter part of 1879 and the early part of 1880 saw the first use of telephone numbers at Lowell, Massachusetts From 1930s until the 1950s, as telephones and automatic switching became widespread, telephone numbers began to increase in the number of digits that had to be dialed In addition to telephones, they now access other devices, such as modems and fax machines. The latter part of 1879 and the early part of 1880 saw the first use of telephone numbers at Lowell, Massachusetts From 1930s until the 1950s, as telephones and automatic switching became widespread, telephone numbers began to increase in the number of digits that had to be dialed BASIC TELECOMMUNICATIONS

5 Because the switches were hard-wired together and fairly hard to re-wire, telephone exchange buildings in many larger cities in North America were dedicated to circuits that began with the first two or three digits of the standard 7 digit phone numbers. From the 1920s on most urban areas had "exchanges" of two letters, followed by numbers, e.g., EDgwood-2519, IVanhoe Later as more digits were added, numbers with the familiar seven digits were used, like GRanite Because the switches were hard-wired together and fairly hard to re-wire, telephone exchange buildings in many larger cities in North America were dedicated to circuits that began with the first two or three digits of the standard 7 digit phone numbers. From the 1920s on most urban areas had "exchanges" of two letters, followed by numbers, e.g., EDgwood-2519, IVanhoe Later as more digits were added, numbers with the familiar seven digits were used, like GRanite BASIC TELECOMMUNICATIONS

6 Certain number combinations were not amenable to this naming process, such as "57," "95" and "97” It was in part due to this factor that telephone exchange names were finally abandoned, since more numbers were needed to prevent a given Area Code from running out of available numbers Certain number combinations were not amenable to this naming process, such as "57," "95" and "97” It was in part due to this factor that telephone exchange names were finally abandoned, since more numbers were needed to prevent a given Area Code from running out of available numbers BASIC TELECOMMUNICATIONS