In a cross-connect system, test pattern insertion circuits are connected respectively to input line circuits to receive a sequence of frames each containing an idle timeslot and a sequence of data timeslots. Each insertion circuit is enabled at multiple frame intervals to insert a test pattern into the...http://www.google.fr/patents/US5351232?utm_source=gb-gplus-shareBrevet US5351232 - Path monitoring system for cross-connect system
