Bags , your Rayburn man reminds me of the time I took back an early model of scanner to PC World. It would not speak to the PC, nor vice versa, and I had sussed out the reason, - sorry - technical diversion here (-thanks to DH talking so much about his current telemetry work on the pipeline bringing oil to Grangemouth from the offshore drills, which involved a lot of oil-pipe substations talking to the main control panel and the other way round. Each piece of equipment had an interrupt request number (IRQ) and the central processor went round all of them in turn, checking on whether they had any data to transfer. The results went into a continually updated monitor screen, where the viscosity, flow speed, temperature and so on of the oil at all points could be checked at a glance - so all the equipment had to work together )
To cut that long story short - the scanner manual said that it had a choice of IRQs x y and z, and the PC said that IRQ numbers x y and z were already in use by other equipment.
At the customer desk I said simply that it would not work with my PC, and was fobbed off with some story which meant that it was my fault I could not get it to work and to go home and try again, so I told them it was a question of incompatible IRQs. His eyes went blank at this unfamiliar term, and he took it into a back room to a supervisor.
I got my money back.