The Tektronix 067-0589-00 Rigid Plug-In Extension is used for operating 7000-series plug-ins outside the mainframe for repair, maintenance and calibration. It is based on a printed circuit board and has a guide rail holding a single-width plug-in. The high-speed signals (vertical, trigger) are carried by coax cables that have BNC couplers in the middle, allowing the signal path to be interrupted for measurement, or to feed an external signal into the mainframe.