[personal] UK Computer Museum on TV

Thanks for that. Yes a long time ago. More likely a 1301. When the 1301s were being phased out they had to connect a pair of 7 track decks to the 1301s to transfer data to 1900. If they'd had 1900s with TM4s they would surely have chosen that route instead. I presume you mean the contacts with the dash-pot attached, not the switches at the end of arm's travel as these are fairly bullet proof. Now I've said that, they will of course fail next week! I was chatting to a friend who was an ICT field engineer yesterday and he said 'we must clean the vacuum chambers sometime'. I asked him how often they should be cleaned and he said at the start of every morning shift. This made us both grin because they have not been cleaned since about 1977 and they are still not causing any problems, we can read tape last written at that time too, though the writing logic 'runs away' for some reason. They were popular on 1301s too, though no TM2 equipped 1301s have survived. They had four times the throughput of the TM4 decks as they used 8 data bits per frame plus 8 cyclic redundancy check bits. The tape moved as 150 inches per second too compared with just 75 on the TM4s giving 90k digits per second compared to 22.5k on the TM4. Still 300 bits per inch on each track though, seems very low density by today's standard. Roger Holmes.