Carousel memory
Carousel memory is a type of secondary storage for computers, which was created by Swedish computer engineers and Gunnar Stenudd. It was first shown at an exhibition in Paris in 1958. Description. The FACIT ECM 64, manufactured by Swedish company Facit AB, is a prototype of carousel memory. To avoid having a single, long magnetic tape, it instead has 64 small rolls of each, with wide tape on each roll, divided into per roll. The tape speed is . To read a particular roll, the carousel rotates so the desired roll ends up at the bottom. A counterweight sits  at the free end of the tape, and facilitates the roll in moving out and down into a mechanism with a read-and-write head. The tape is then rewound. The average seek time is and the storage space is . The control system is operated by transistors. Both the carousel and individual spools are replaceable. The magnetic tape is a 5/8-inch (1.6 cm) wide and 0.05 mm thick Mylar 3M Co type 188.The storage density is specified to , and the access head is capable of simultaneous read/write operations. The power requirement is 3-phase 380 volts 50  Hz, with when in standby and when active. Signaling for data uses -20 V to 0 V 5 µs pulses. Peak transfer speed is , using 8-parallel lines and thus per line. The first delivery of the Facit EDB 3 computer in 1958 (to ASEA in Västerås) used the carousel memory Facit ECM 64.