Abstract: A communications device is used for transferring data to and from a data processing system. A controller in the communications device responds to communications signals from a signal source associated with the data processing system. A standard option connection is interposed between the controller and the signal source. When an option device is to be used, a circuit board is positioned in the connection. Conductors on the circuit board control the transfer of signals between the communications device and the signal source. The option device also includes data handling circuitry that responds to signals on the conductors or that may interrupt and/or modify these signals. The board also controls an option present signal used by the communications device for control purposes.