The 9-Pin Protocol is a two-way communications protocol for the RS-422 D-sub electrical connector interface, in which a bi-direction signal is transmitted over a single, four wire, serial cable to allow the remote control of a wide variety of devices including, reel-to-reel type C videotape video tape recorders (VTR) as well as videocassette recorders (VCR).
The online editing control units used in post-production relies heavily on the 9-Pin Protocol to remotely control auotmated linear editing devices that use sequential access methods.
In broadcast automation the Video Disk Control Protocol (VDCP) use the 9-Pin Protocol to playout broadcast programming schedules.