Data generated at a telecommunications network switching node is selectively delivered to one or more data receiving device (e.g., data "collection box") connected to the network, and command and control signaling is transmitted from the data receiving device to the switching node. This bi-directional communication is carried out in a manner compatible with voice grade lines. In an exemplary application, call identifying information, referred to in the TIA/EIA Standard as CDC (Call Data Channel) Messages, is delivered from an Intercept Access Point (IAP) switch that provides telephone service to a subject of an authorized surveillance order, to a law enforcement data collection box, utilizing Frequency Shift Keying (FSK) signals. Control signals are sent from the data collection box to the IAP switch utilizing Dual Tone Multi-Frequency (DTMF) signaling. The state of the art is advanced, and a contribution is made to law enforcement and other fields, as the invention allows replacement of costly and lengthily provisioned data delivery circuits, such as ISDN lines or private digital data circuits, with widely available and less expensive voice-band data delivery equipment.