From Longman Dictionary of Contemporary Englishoutside line/call etcoutside line/call etcTCTa telephone line or telephone call which is to or from someone who is not inside a particular building or organization Dial ‘9’ before the number when making outside calls. → outside
Examples from the Corpus
outside line/call etc• Caroline Amphlett had left and it was switched through to an outside line.• Each telephone instrument had its own dial and from it can be dialled other extensions as well as outside calls.• She concentrated on the outside call.• There's a private telephone in the compartment in front of you if you need to make any outside calls.• A few telephones had direct outside lines when the switchboard closed down at night. 