The term “Pulse Code Modulation (PCM)” refers to a digital scheme used to transmit or record analog data (Shi and Sun 17). PCM signals are binary in nature. This means that two states (logic 1 and logic 0) are only possible during the digitalization process. The scheme makes it easier for technologists to digitalize a wide range of analog data. Some of the targeted data include analog voices, motion pictures, Virtual Realities (VRs), and telemetries. In order to obtain quality PCM, analog amplitudes are measured regularly. The amplitude is then rounded off to a predetermined level (or unit) in a process known as quantization.
Pulse Code Modulation is an efficient method that makes it easier for individuals to sample and digitalize analog signals. The PCM scheme is embraced because of its advantages and applications. To begin with, the method is appropriate whenever transmitting information for long distances. This is the case because digitalized signals might not be interrupted or lost. The scheme makes it possible for human beings to transmit signals efficiently (Gupta et al. 2190). Digital signs can be conveyed accurately, thereby delivering the intended message efficiently. PCM is also beneficial since its immunity to noise is quite high. Because of these advantages, the concept has been applied in a wide range of fields. For example, PCMs are used in space shuttles and telephony. Digitalized signals can be stored in different formats such as compact and portable discs.
The original PCM concept is attributed to Moses Farmer. He was the first American innovator to sample and transmit digital signals in 1853 (Spilsted 12). In 1903, an engineer named W. M. Miner managed to apply the idea of time-division multiplexing (TDM) to telephony. By 1920, image samples could be conveyed using telegraph signaling techniques. The original idea of PCM was conceived by Alec Reeves in 1937. During the Second World War, the Allies developed a powerful encryption machine named SIGSALY. The equipment could transmit high-level communications messages during the period. In 1949, the concept was developed by Ferranti Canada in such a way that it could transmit radar data.
Within the past five decades, numerous inventions have emerged in different parts of the world. The first PCM recorder was designed in 1967. The recorder could be used to store signals on video tapes (Spilsted 56). In 1973, Nikil Jayant, P. Cummiskey, and James Flanagan developed the famous Adaptive Differential Pulse Code Modulation (ADPCM). Competent engineers managed to introduce the compact disc (CD) in 1982 (Spilsted 73). Every CD is capable of storing eighty minutes of digitalized audio information or data.
Usage in Digital Audio
Bhardwaj defines the term “digital audio” as a signal that is recorded through a process known as digitalization (26). Basically, the concept is used to define the technology of sound production and recording using encoded digital formats. The process through which digital audio is produced borrows a lot from the PCM concept. That being the case, PCM is embraced in digital audio to translate analog signals using powerful quantization processes.
The above process ensures that analog signals are translated using a binary language (Shi and Sun 43). Digitalized signals can be processed further using a technique known as digital data compression (DDC). After quantization, the signals are encoded in order to make them retrievable or usable. This discussion shows conclusively that digital audio is something that has been catalyzed or supported by the PCM concept.
Bhardwaj, Tarun K. “Generalized Digital Pulse Code Modulation and its Comparison with Other Compression Schemes.” International Journal of Emerging Trends & Technology in Computer Science, vol. 3, no. 3, 2014, pp. 25-29.
Gupta, Akash K, et al. “Study on Performance Analysis of Pulse Code Modulation (PCM)”. International Journal of Advanced Research in Electronics and Communications Engineering, vol. 5, no. 8, 2016, pp. 2189-2193.
Shi, Yun Q., and Huifang Sun. Image and Video Compression for Multimedia Engineering: Fundamentals, Algorithms, and Standards. 2nd ed., CRC Press, 2017.
Spilsted, Kamal. Pulse, Code, Modulation. AuthorHouse, 2014.