A field engineer is a one-person operation with a vehicle for a warehouse and a customer's doorstep for a counter. Whatever they cannot do on site becomes a phone call, a second visit or a job written up from memory three days later.
The trades differ less than you would expect. An HVAC technician scanning a rooftop unit, a pest control technician leaving a treatment record, an electrician producing a test certificate and a lift engineer tagging an inspection all need the same four things: identify the asset, record the work, account for the parts, and leave the customer something official.
What changes between them is the document and the label. That is what decides whether a belt-worn receipt printer is enough or whether a full-page printer belongs in the van, and whether an asset label has to survive a plant room for a year or a rooftop for a decade.
Anything the engineer cannot complete on site turns into a second visit, and the second visit costs more than the hardware did.