Data transmission equipment - comprises transmitting units television receivers and key code units

摘要

Data transmission equipment using the inter-band frequencies of television transmissions, comprises a transmitting station with its transmitting units (41) and aerial (42). It also comprises receivers with their aerials (43), television receivers (44), data units (45). Other parts of the equipment have key code receivers with their aerial (46), television receivers (47) and key code units (48). The transiting station sends burst of data from channels. The data is time multiplexed. Each burst has a prefix containing a code signal, synchronising signal and usual signals. The receiving station can receive the date information and compare this information with booking information. If the date information and the booking information are compatible, a validation signals are sent by the key code receivers.