For normal dial-in operation, the terminal operator calls the communication controller or communication adapter, and VTAM® is notified of the incoming call. The NCP then requests that the physical unit identify itself. When the physical unit responds, VTAM locates the proper physical unit definition in an active switched major node. After VTAM completes activation of the physical unit and its subordinate logical units, sessions involving the logical units can be initiated as if the line were nonswitched.

Switched lines with dial-in capability can allow or disallow incoming calls. For an incoming call to be allowed, the line must be in answer mode. The mode setting can be specified in the definition statement for the line and can be changed with the ANS operand of the VARY ACT command when activating the line, or with the VARY ANS command after the line is active.