Wikipedia
Fbus (for "Fast Bus") is an ANSI/ IEEE data bus oriented towards backplanes and cell phones. The standard specifies a way for various pieces of electronic hardware to communicate, typically with one piece acting as master (sending a request), and another acting as a slave (returning an answer). The F-Bus is a bi-directional full-duplex serial type bus running at 115,200 bit/s, 8 data bits, no parity, one stop bit (8N1). Much like a standard RS-232 serial port, F-Bus connections use one pin for data transmit, one pin for data receive and one pin for ground.
The Fastbus standard specifies completely the size, power requirements, signalling levels, and communications protocols for boards that live in a Fastbus crate, which is also a part of the specification.