An operator-assisted call is one in which the calling party places a telephone call which requires an operator to provide some form of assistance in completing the call.
This may include telephone calls made from pay phones, calls placed station-to-station, person-to-person, collect, third number calls, calls billed to a credit card, and certain international calls which cannot be dialed directly.
The telephone operator may also be able to assist with determining what kind of technical difficulties are occurring on a phone line, to verify whether a line is busy (Busy Line Verification, or BLV), or left off the hook, and break in on a phone line to request for the caller to clear the line for an incoming call (Busy Line Interruption, or BLI).
An operator-assisted conference call or op assist call is one in which the conference call is managed by an operator. The telephone operator will greet each call participant, gather specific information from each participant, introduce key speakers, and manage questions and answers, all from the telephone.