Method for signal transmission while a call is in progress in telephone switching systems interconnected as main and secondary systems

摘要

Signals can be transmitted while a call is in progress when a speech gap occurs. A speech gap is identified with analog/digital converters which are connected to the speech path at both ends of an extension line. This is done by comparing received digitised speech signals with a stored, pre-defined minimum value. During the signal transmission, the speech path is temporarily interrupted. The analog/digital converters remain connected to the speech path in order to identify a speech transmission restart so that the signal transmission can be aborted at once in order to re-establish the speech connection immediately.