The Sony Helical SV-201 was the world's first transistorized VTR. The system used two heads and a half wrap around the heads, turning at 1800rpm (Half a revolution one TV field) at a tape speed of 7.5 ips (the same speed as an audiotape recorder). Since the two-head system was not acceptable for broadcast use and the machine was too large and expensive for consumers, Sony decided to branch it out into the industrial, educational and medical applications market.