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I'm interested in a description of the mechanism or pictures of the mechanism that stops water entering the air-intake of a jetski. I have seen video of riders going fully underwater for a couple of seconds on jetskis.

Several months ago I bought a Lexmark "Prevail" PRO705 all-in-one printer at PC World in the UK (£129.99). It has worked well and I like the WiFi etc...

Now one of the reasons I bought it was that I was told by the PC World printer guru that it had very low cost black cartridges, so I bought two extra black cartridges, as we do quite a bit of black printing. The cartridges bought were '105XL' and the cost £4.88 each.

The just ran out of the first (supplied with the printer) cartridge.. So I unpacked one of the 105XL's and installed it. Printer then announced is was 'black cartidge not supported by this all-in-one printer', so I tried again, same results - then I noticed the original supplied cartridge was labelled 100XL. Apparently the 105XL's are for the PRO805 and PRO905 printers.

Now I have a good little laboratory here and I have measured the casings of both cartridges and they are almost exactly the same (certainly within the tolerances of injection moulded plastic). There are no electrical connections to the cartridge at all visible.

So finally here is my question:

How do Lexmark know that the cartridge is different?

Is there an RFID tag inside?

Does it use some other device (optical reader? - couldn't find any evidence).

Is there a way round it?

NB: I'm not some sort of cheap-skate, but I feel aggrieved that I was mislead and bought an expensive printer on the promise of cheap black ink (without resorting to refills). The 100XL is three times the price of the 105XL!