 In 1961 Oktava introduced the D2 miniature telephone and began supplying dynamic microphones to the Kremlin.The plant also commenced a second round of modernisation and began producing electro-acoustic measuring instruments to test microphones and telephones.From 1964 Oktava began implementing a "zero-defect" production system, and their TM-4 miniature telephone and ML-16 ribbon microphones received state quality marks.