Which ISDN feature allows for multiple calls to be transferred to another line?

The feature that allows for multiple calls to be transferred to another line is called call transfer. This function enables a user to divert an active call to another line, facilitating the continuation of the conversation without disrupting the communication flow. In the context of ISDN, it is particularly useful as it allows for the efficient handling of multiple incoming calls.

Call transfer can be essential in situations where a user needs to pass a call to a colleague or an available line, ensuring that calls are not missed and can be addressed by the appropriate party. This capability enhances the management of communication within organizations.

While the other features are related to call handling, they serve different purposes. Call forwarding directs calls to another number but does not involve transferring an active call; call waiting alerts the user about an incoming call while they are already on a call, allowing them to switch between calls without transferring; caller ID simply displays the number of the incoming caller but does not manage call flow. Each of these features plays a role in call management, but call transfer is specifically designed for the purpose described in the question.