Graybeards remember when RS232 breakout boxes and protocol analyzers ranked as ninja tools for commissioning PI System interfaces.
Ideally there was a dedicated port for the interface and cabling was a simple matter of determining DTE or DCE pin out. For alarm printers we would customize a Y cable so the PI System could eavesdrop on an existing serial link (PI event logger and PI UFL stream loader are the usual interfaces). In this latter configuration the trick was to snip the transmit wire to help avoid a signaling disturbance returning from the interface node that could lock up the printer, fill print buffers and generally get you in hot water with the operators.
Fast forward to unidirectional security gateway technology. The data transmission path is usually provisioned with a single strand of optical fibre. Network security enforcement is simple because the destination system has no return into the protected network.
So there it is - a simple idea for security that is too good to just fade away. Can it really be that simple? Hear all about it in a Webinar on Thursday, September 15, 2011 "Strong Cybersecurity: Power Plant Case Study" from vCampus members Andrew Ginter of Waterfall Security Solutions and Denis Kilgore of DLL Solutions.