The CTI BUS (Computing Terminal Interconnect Bus) was developed for and used on the Professional 300 Series of DEC PDP-11 personal computers solely. It seems to be a variant form of a QBUS, with some additional signals, carried on a connector with a different physical form factor (a 90-pin zero-insertion-force connector, of which the first 60 pins are used for the CTI BUS).
In most cases, the bus will allow option modules to be placed in any available option slot. Each option module can generate two different hardware interrupt signals. When an option is in place, an option-present signal is asserted. Each option contains onboard ROM with identification information.
- Professional 300 Series Technical Manual (EK-PC350-TM-001) - see Sections 5.3.3, "Buses", and 220.127.116.11, "CTI BUS Interface Circuits"