?field technitian?job ,wit h AS /400

?field technitian?job ,with AS /400

I am applying or a ?field technitian?job in a government institution.

Although I have a CompTIA A+ certification, with 2 years experience.I do not have an associates degree, or know anything about AS/400 series are IBM servers. what they are asking for.

Iv seen the long list of AS/400 certifications on IBM site.

Should I admit its over my head,or can you suggest URLS,to read up for interview.