{HEAD ~ External hardware} that connects to I/O devices such as sensors, motors, monitors, machines, etc. can be connected to {TAIL ~ the invention} via I/O boards that receives and transmit digital signals, representing control information, to the bus 
connected to
{ HEAD ~ External hardware } that connects to I / O devices such as sensors , motors , monitors , machines , etc . can be connected to { TAIL ~ the invention } via I / O boards that receives and transmit digital signals , representing control information , to the bus
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH