Rai Radiotelevisione Italiana

Mario Cominetti

Alberto Morello

Digital characters are broadcast by grouping the characters into a series of blocks, and providing each block with a synchronization character and an identifying prefix to form a digital package. The characters in the prefix provide information on the identity of the series, the overall number of packages which form the series, and the number of each package in the series. The characters of the various packages are converted into a 10-bit serial data format which includes one start bit, one stop bit and eight data bits. The serial data is transmitted in synchronous succession, encoded into a differential two-phase signal, and modulated onto a carrier frequency for broadcasting. The reception apparatus comprises a receiver, a digital computer and a connecting interface between the receiver and the serial input of the computer. The interface includes a bit clock signal generator for detecting the mid-bit transitions of the differential two-phase signal to produce a clock signal, a two-phase decoder comprising an EXOR gate driven by the differential two-phase signal and by the clock signal to provide a differential output signal, and a differential decoder comprising an EXOR gate and a delay circuit both driven by the differential signal, with the output of the delay circuit driving a second input of the EXOR gate to provide as output a digital signal representing the broadcast characters.

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San Mauro Torinese, Italy

Mario Cominetti