She was fitted with many sophisticated radio and electronic devices, such as a Kasatka satellite downlink that provided targeting information. A powerful target guidance radar measuring more than 100 square feet in area was built into the forward edge of the sail structure. The radar was deployed from the front of the sail, which opens by rotating 180 degrees.
Original plans called for 35 of these submarines to be built, augmenting nuclear-powered Project 675 (ECHO II) class boats. (The ECHOs were an enlarged nuclear version of the Juliett with 8 missile launchers.) Only 16 Julietts were actually built; most were produced by a shipyard in Gorky between 1962 and 1968.
Six submarines were assigned to the Northern Fleet, six were split between the Baltic and the Black Sea and four were assigned to the Pacific Fleet. In 1987, all the Northern Fleet boats were re-assigned to the Baltic Fleet.