Remote provisioning of telephone channel unit using inband digital code sequences transmitted over tandem link

To remotely interrogate a telecommunications services channel unit resident in any office along a tandem network communication link, a control link establishment code sequence comprised of one or more sets of predefined digital code bytes is transmitted from a test system controller. The format of the control link establishment sequence is such that as it is forwarded down the link, any tandem channel unit or units that are intermediate the test system controller and the destination channel unit will transition to a transparent state, so that only the destination channel unit will be able transition to an interrogation, response mode. During the command-response mode, channel units connected in tandem between the selected channel unit and the interrogating test system controller continue to assume a transparent state, so that command and response messages propagate unmodified through such intermediate channel units. A command message may contain information for defining the operational configuration of the selected channel unit. It may be used to read the operational configuration or status of the selected channel unit, or it may contain supervisory control information for directing the selected channel unit to conform with a prescribed operational condition.