The tax status will depend on several facts not stated in the original post. From the OP's "handle", I assume that (a) he/she is a US citizen, (b) has a permanent residence in the USA, (c) does not own or rent a residence in CH, and (d) does not spend more than 183 days per year in CH. (If any are not correct, please tell us?)

On that basis, I respectfully I disagree with Scrambled (and invite his/her reply).

Per Article 15 of the US-CH tax treaty ("Dependent Personal Services"), the income is taxed according to where the services are performed:

"wages...derived by a resident of a Contracting State in respect of an employment shall be taxable only in that State unless the employment is exercised in the other Contracting State."

Per the original post, the work will be performed in the USA, thus the wages would not be taxable in CH. If some of the work is done in CH, then that part may be taxable in CH (and in the US).

For clarity (to minimize the number of tax returns), it is best to have a written agreement with the employer specifying that the work is performed in the US, and visits to CH are only for training.