The Modem Manager runs as a server on one system and as a client on others. The server and client Modem Managers cooperate to provide the modem pool management and to set up data paths between modem users and the allocated modem.

Incoming and outgoing calls are referred to as "tasks". When an outgoing call (or task) is requested by a workstation on the network, the Modem Manager will determine if a modem is free, select an unused modem, and dial the call. If the Modem Manager determines that all modems are currently in use, the call will be queued until a modem becomes free.

The queue operates on a time priority basis. If an outgoing call is attempted and fails, the call is not sent to the tail of the queue, but is slipped into the queue according to the parameters configured within its configuration file settings (see "VTS Programmer's Guide:  Config.ini [SYSTEM] Section Settings for the Modem Manager"). For example, if a call is attempted and fails, and has been configured to be redialed in one minute, then the call will be slipped into the queue appropriately.

The modem selected by the Modem Manager to perform the outgoing call may be on a different workstation from the task requesting the call. The Modem Manager sets up transparent data paths between the modem and the requestor. In the event that the Modem Manager fails to complete the connection, it can retry the attempt using alternative modems (if available).

When an incoming call is received, the Modem Manager passes the initial data to tasks that have previously registered an interest in incoming calls. If a task accepts the offered call, then the Modem Manager will set up transparent data paths between the modem and the recipient. If no one accepts the call, then the Modem Manager will return the call to the operating system to allow other applications the opportunity to take the call.