DATA TRANSMISSION SYSTEM CAPABLE OF RESPONDING TO TERMINAL REQUET

摘要

PURPOSE:To transmit picture data at low cost, by frequency-multiplexing updating data obtained as a result of retrieving a data base in response to a request from a user terminal and fixed data by carrier different for each data send on a transmission line. CONSTITUTION:When a request is made to a center from a terminal through a coaxial transmission line 2, the request is processed by a videotex CPU through an RF MODEM and a request processing CPU and a picture file 1 is retrieved so as to detect the requested data. The data are modulated by an RF modulator 3a as updating data. Irrespectively of the request from the terminal, fixed data are also supplied through a fixed data CPU and the fixed data are modulated by another RF modulator 3b. The updating data and fixed data are respectively carried on by different carrier and sent to the coaxial transmission line 2 after they are frequency-multiplexed by means of a mixer/ branching filter 4. Therefore, numerous picture data can be transmitted at low cost.