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PEDQ 3005/4005/5005 QMX
Changing service information
The transport stream contains data in the form of tables that the receivers evalu-
ate and require for convenient use. The TP module can change the "Network
Information Table" (NIT). The "NIT" contains data that is required by the set-top
box for the automatic search feature.
2.3.3 Explanation of the term "symbol rate"
Modulation methods such as QPSK and QAM transmit multiple bits simultane-
ously. These are referred to as symbols. Error correction bits are transferred in
addition to the user data stream which transmits video and audio information.
The FEC number specifies the ratio of error correction bits to user bits.
Processing small symbol rates
A low data rate means that the output symbol rate will be very low. With some
digital receivers, this may cause reception problems. This can be remedied by
using the stuffing option to set the QAM modulation to a higher value.
Defined symbol rates
Some cable operators specify a fixed symbol rate (e.g. 6900 kilosymbols per
second).
