IEEE Policies

9.21   Standard Telephone Formats 

The following is the correct format to be used when listing telephone numbers in all IEEE publications and correspondence:

+CC  NDC  SN

where:
CC is the country code ( 1 to 3 digits)
NDC is the national destination (area, city, etc.) code ( 0 to 3 digits)
SN is the subscriber number (up to 10 digits but typically 6 to 8 digits)

Grouping of digits within a number may be accomplished with spaces rather than dots or hyphens.

Examples:
Aveiro (Portugal): +351 234 234321
Hong Kong (SAR, China): +852 9 988 1234
New York (USA): +1 213 765 4321
Paris (France): +33 1 44 331234
Rio de Janeiro (Brasil): +55 21 98765432

The phone number is preceded by a "+". The "+" represents the international access code needed to access the international trunk line which is different for each country, for example in the United States it is "011" and in Belgium it is "00". No other punctuation should be used.