International Switching
	The first I.S.D. (International Subscriber Dialling) call was made by the Lord Mayor of London (Sir Ralph Perring) at 11am on 8th March 1963. Calling from Fleet Building, he dialled 13 digits and was connected to Monsieur Jacques Marette, the French Minister of Posts, Telegraphs and Telephones, in Paris.
| EXIT | Faraday | Wood Street | Wren House | Stag Lane | Caroone House |

The overseas telephone service dates back to the early 1900s and this needs further research for inclusion on these pages. All calls in those early days were manually connected and growth in traffic centred on Faraday International Telephone Exchange. 

Overview

In the early days, international calls were connected via the manual switchboard with all the associated equipment in the same building, called an International Switching Centre (ISC).

As technology developed, calls were controlled by the operator dialling over semi-automatic routes, with the switchboard remote from the switching equipment. Thus the operators worked in an International Control Centre (ICC), some distance from the ISC.

Exceptionally, it was sometimes convenient to house the ICCs and ISCs in the same building. The more general term of International Telephone Services Centre (ITSC) was used to reflect this, but even then, the name ISC was commonly used to mean both.

As signalling and switching equipment evolved, subscribers could dial their own international calls via the automatic equipment in the ISC and this service was named International Subscriber Dialling (ISD). From (about) 1978 this was changed to International Direct Dialling (IDD) to reflect the fact that you didn't have to go via an operator. 

The History & Growth of ISD

The growth in International Subscriber Dialling (ISD) relied heavily upon:

• Supplies of suitable switching equipment.
• Compatible signalling equipment.
• Accomodation to house both staff & equipment.

The Register-Translators of the Director Areas were particularly suitable for sending long digit trains of pulses (e.g. up to 15 numbers) and thus ISD facilities were first introduced in London.

International traffic was originally centred on the Faraday Building and spread to a number of nearby, suitable locations as the demand for ISD increased rapidly over the years.

Wood Street was the next major centre which began as an extension to the old Wood Street telephone exchange.

As growth continued, Stag Lane was brought onto line as a stop-gap measure while Mondial House was still being built.

During the 1980s Caroone House was the administrative centre for International Telephones, as the division was known.

Goonhilly Downs provides satellite and submarine cable links with the rest of the world.