International Direct Dialling was introduced in the 1970s, so calls can be dialed by country code without an operator.

International Direct Dialling (see the List of country calling codes)

Calls could also be made using the full international dialling code since the introduction of International Direct Dialling.

IDD (international direct dialling)

The term was extended when, on 8 March 1963, subscribers in London were able to directly dial Paris using International Direct Dialling.

Also, international direct dialling was being introduced and as other countries (such as the USA) had different assignments of letters to digits the opportunity for confusion existed.

Calls to and from Malaysia do not require international direct dialling (IDD) codes, a legacy of when Singapore was part of Malaysia until 1965.

The system can be instructed to prevent individual extensions from making certain calls such as IDD (international direct dialling) and STD (subscriber trunk dialling).

International Direct Dialling (IDD) is provided, and Gibraltar was allocated the access code +350 by the International Telecommunication Union.

These included a refusal to recognise International Direct Dialling (IDD) code which restricted the expansion of Gibraltar's telephone numbering plan, and the prevention of roaming arrangements for Gibraltar's GSM mobile phones in Spain.

With the introduction of International Direct Dialling in the 1970s, Gibraltar was allocated its own IDD code of +350 by the International Telecommunication Union (ITU), which was accessible from any telephone network outside Spain.

The use of alphanumeric codes for exchanges was abandoned in Europe when international direct dialling was introduced in the 1960s, because (for example) dialling WHI 1212 on a French phone would get different numbers to dialling it on a British phone.