At the office location of another person or organization.
- remote (adj)
- off-site (adj)
- offsite (noun)
- telecommute, dial in (verb)
She can fix most server problems remotely, but she'll have to go on-site for this one. (The person will be at the physical location of the server.)
I work on-site three days a week. (I am at the main workplace when I do the work.)