A parallel and user port breakout board allows you to access the data pins of both the parallel and user ports more easily for interfacing projects.
This particular board requires both the parallel and user port connectors to be connected simultaneously as the green output connectors are from the parallel port however the LED indicators that indicate the status of each pin on the parallel port outputs are grounded to the user port ground lines.
It's relatively simple to program the BBC Micro's parallel and user ports with only a handful of lines of BBC BASIC. The video below shows the results of a five minute experiment to program light sequences using the board.
The same software can be used to drive the Deltronics Control IT buffer box which provides the same functionality to the user as this board but with the added protection of overcurrent protection and the bonus of fully powered output lines.