A call-control signal that is transmitted by the data circuit-terminating equipment (DCE) to the data terminal equipment (DTE) to indicate that the connection is available for data transfer between both DTEs. 2. A signal that (a) is sent in the backward direction in the interexchange data channel, to indicate that all the succeeding exchanges involved in the connection have been through-connected, or (b) is sent in the forward direction in the interexchange data channel to indicate that all the preceding exchanges involved in the connection have been through-connected. Note: The ready-for-data signal is sent by the user terminal. It corresponds to the ready-for-data state at the user interface.