Complex sentence: The P-15 radar was upgraded to the point where it received a new designation, the P-19 "Danube", this new radar completed state trials and was accepted into service with the Soviet Air Defence Forces from 1974.
Split into simpler sentences: The P-15 radar was upgraded to the point where it received a new designation, the P-19 "Danube". This new radar completed state trials and was accepted into service with the Soviet Air Defence Forces from 1974.