Videotape was introduced in 1956 with the Ampex Quadruplex system. The programmes were recorded onto 2-inch Quadruplex videotape. The VR-8000 was made using a similar chassis used by Ampex's 2-inch quadruplex VTRs. The roles of quadruplex structure in translation control are not as well explored. This was before 1956 when Ampex introduced the first Quadruplex videotape recorder (VTR) VRX-1000. The Ampex video system is now obsolete, but many thousands of quadruplex videotape recordings remain. This was further developed into the quadruplex telegraph by Thomas Edison. From 1961, RTS began to use quadruplex video tape recording equipment. Such a quadruplex is described as tetramolecular, reflecting the requirement of four separate strands. It has been suggested that quadruplex formation plays a role in immunoglobulin heavy chain switching.