Interactive country-wide data transmission system for serving stationary and mobile, battery powered subscriber's units

In a two-way interactive communication video network having a network switching center (2) for point-to-point communications between subscribers at different geographic locations, a local base station (3) configuration is provided for facilitating low power battery operated portable subscriber units (17). The local subscriber units surrounding a base station are adapted for multiplex transmission of digital messages synchronously related to a broadcast television signal for system coordination. Digital messages are transmitted from the local subscriber units to the base station data processing facility through a set of receive only cell site subdivision zones distributed over the base station transmitter geographical range, which communicate with the base station data processing facility over a communication link such as wired cable. Messages are compiled and relayed by satellite to a network switching center transmitter site for nationwide point-to-point communications. Small-size, inexpensive, low-power, portable, digital-transmitting subscriber units are introduced compatible with interactive video data system standards with the ability to cross subdivision and cell zones. Thus, monitoring of inventory, temperature, and other parameters for passive automatic alarm systems and the like, as well as active mobility of subscriber units for meter reading and the like is made possible with direct low-cost nationwide real time reporting capability.