h Pre-emphasis of sound signals According to CCIT Recommendation J17 Sampling frequency 32kHz Initial coding of sound signals 14 bits/sample linear PCM Companding Quasi instantaneous with compression to 10 bits/sample in 32 sample blocks Error protection Parity check of six most significant bits by adding a parity check to every 10-bit sample Frame format Frame length is 728 bits/millisecond (frame sync word 8 bits, control word 5 bits, additional data 11 bits, sound data 704 bits) Bit rate of sound and data 728kbit/s Transmission method of digital Frequency multiplex by introducing an additional sound carrier at 5.85MHz (systems B, G) or audio information and data in a 6.552MHz (system 1) from vision carrier composite video signal Type of modulation of additional Four positional phase shift keying (DQPSK) i.e. differentially encoded QPSK sound carrier Spectrum shaping 100% cosine roll off split equally between transmitter and receiver (overall bandwidth of digital signal approximately 728kHz) Scale factor signalling By modification of 9 parity bits per scale factor bit, detected by majority decision logic (3 bits per sound coding block, two blocks per frame) Bit interleaving (sound data) 44 X 16 (frame alignment word not interleaved) Energy dispersal scrambling By modulo two addition of a pseudo-random sequence of length 2°-1 bits synchronously with the multiplex frame. Frame alignment word not scrambled 57/18 Video transmission Distribution (with final connection Trunk Studio Hub site External feeds Distribution (with final Head end Super trunks connection Local aerials Figure 57.19 Tree and branch cable TV network coaxial cable were replacing the original multi-line twisted pair Homes Passed. The number of residences which could be con- systems, and enabling more TV channels to be carried, SO 'out of nected to a cable TV system, given the existing extent of its area' broadcasts, satellite receptions and tape based channels could build, i.e. those needing just a final cable drop into the home. be added. Modern 