Around about 1985/6 when I was doing my electronic engineering apprenticeship at Link-Miles in the UK (flight and vehicle simulation), we had a requirement to l

Around about 1985/6 when I was doing my electronic engineering apprenticeship at Link-Miles in the UK (flight and vehicle simulation), we had a requirement to link together various bits of RS232-connected equipment as needed and between rooms and labs that were spread around the site - for example, we needed terminal comms from our PCs to a VAX 11/750 and various serial printers, plus we had custom equipment racks around the place (including Meiko Transputer development systems!) and also serial-connected device programmers (PROM/EPROM/PAL/GAL) and so on. After a bit of digging, I found 'Infa Communications' and their 'Infaplugs', which carried serial traffic round a ring of 75 ohm coax between the plugs. The system also had a simple connnect/disconnect command language (similar in principle to the Hayes/AT modem command set), so I wrote a TSR (terminate and stay resident) 'switchboard' program in Turbo Pascal, which allowed users to change link destinations as required, and could also intercept terminal comms so that print streams coming from the VAX to the local terminal could be grabbed and redirected to elsewhere - you could even program an EPROM in the lab from your office desk (although you'd have to phone and ask someone to pop one in the Stag programmer!). It was all very cool for its time and avoided the need for dozens of long runs of screened multicore cable and multiplexers all over the place - it all worked very well, but then came the familar sight of thick yellow Ethernet coax everywhere and the writing was on the wall for the Infaplugs.