i use 311 because my lead didnt function with 409
didnt seem to be much difference between the two though feature wise.
just a regular dual k obdc parallel cable i have from ebay for 25quid at the time
like it says on the site
Release 409 must be used with a modern interface.
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It does not work at all with obsolete interfaces based on opto-isolators (including our own ISO-COM which we discontinued more than 2 years ago).
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Most 3rd party interfaces also use opto-isolators and are therefore incompatible with version 409 of VAG-COM -- use version 311 instead. If in doubt, contact your hardware supplier.