Jawaharlal Nehru Technological University Hyderabad B.Tech IV TELEMETRY AND TELECONTROL Previous Question Paper (September - 2022 - R18)

Error correcting codes are techniques used in digital communication to detect and correct errors that occur during data transmission over noisy channels. By adding redundant bits to the original data, the receiver can identify and fix corrupted bits without requiring retransmission.

Correction is achieved by mapping source data to a larger set of codewords. The receiver uses the redundancy to check if the received sequence matches a valid codeword; if not, it uses the known mathematical structure of the code to determine the most likely original sequence.

Coding gain is the improvement in signal-to-noise ratio (SNR) achieved by using error correction coding compared to an uncoded system for the same bit error rate. Bit error rate (BER) is the ratio of the number of bits incorrectly received to the total number of bits transmitted. A block code is a type of error correction code where a fixed-length block of input data bits is mapped to a fixed-length block of output codewords, processed independently of other blocks.

A pneumatic telemetry system uses compressed air as the transmission medium to convey process information over distances. It typically operates on a standard pressure range of 3 to 15 psi (0.2 to 1.0 bar).

The system consists of a transmitter, a transmission line (tubing), and a receiver. The transmitter senses the process variable (e.g., pressure, flow, or temperature) and converts it into a proportional pneumatic output pressure. This pressure signal travels through the tubing to the receiver, which acts as a controller, indicator, or recorder. The receiver interprets the pressure signal to display or regulate the process variable. These systems are inherently safe in hazardous environments due to the absence of electrical sparks, though they are limited by slow response times over long distances due to air compressibility and line resistance.