The foundations of IN
John R. Anderson · Institution of Engineering and Technology eBooks · 2002
Triggering in intelligent networks is fundamental because the original purpose of th IN was to enable call control software to recognise pre-assigned events and conditions and suspend call processing whilst it obtained further call processing instructions from an external service control point. However, when IN was introduced, the software which handles this 'breaking out' process could not simply be added alongside existing call processing functions. It had to be built in as an integral part of the basic switch call control. In order to achieve progress in building the standard recommendations for enhancing telephone networks with IN features, it was necessary to introduce a hypothetical modelling device known as the 'service switching function' (SSF) to the telephone exchanges.