How to activate Swiss pass on cross-border train?

Hi, I will be travelling from Milan to Zermatt thru Domodossola and I have ordered a swiss pass. Providing swiss pass is valid from Domodossola onwards, I have purchased a ticket from Milan to Domodossola, EC 50. My question now is how do I validate my swiss pass on this route?

I have read different comments re swiss pass activation. Some people say can only activate at swiss train station and some people say the pass can be activated on the cross-border train by a swiss train conductor? Is there a offical site that I can confirm this?

Is Swiss Travel System the authority on this? Quote from the FAQ on http://www.swisstravelsystem.ch

16) How do I activate my Swiss Pass? (applies to Open Date Passes only)You can validate the Swiss Pass together with your Pass at any larger railway station throughout Switzerland. Please note that you need to validate your Pass before making your first journey. If you are travelling to Switzerland by train the conductor will activate your Swiss Pass.

Yes, Swiss Travel System is the authority. So, as you can see, the conductor can validate your Pass at the border (while you are on the train)

Thanks Kim! Just want to make sure i won't get into trouble if I just stay on train :-)

The travel agent which I purchased the Swiss Pass from insist that I have to activate the pass at a swiss train station before use...

I think that used to be true but no longer is. The idea of making visitors jump off the train and run into the station finally became just silly, I guess.