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Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
pumping process for achieving population inversion and gain in a laser medium; process for providing energy to an arbitrary nonlinear optical system; process in which input energy is used to obtain a population inversion in a laser medium. punched card a method, now obsolete, used to represent data and programs as cardboard cards where the values were represented by punched holes at appropriate places. punctured code a code constructed from another code by deleting one or more coordinates from each codeword. Thus an (n, k) original code becomes an (n - 1, k) code after the puncturing of one coordinate. punctured convolutional code a code where certain symbols of a rate 1/n convolutional code are periodically punctured or deleted to obtain a code of higher rate. Because of its simplicity, it is used in many cases, particularly in variable rate and high-speed applications. Compare with punctured code. puncturing periodic deletion of code symbols from the sequence generated by a forward error control convolutional encoder, for purposes of constructing a higher rate code. Also, deletion of parity bits in a forward error control block code. pure ALOHA type of multiple access protocol. Any user is allowed to transmit at any time. The possible collisions result in destroyed packets. Destroyed packets are retransmitted at a later time. See also ALOHA. pure longitudinal wave ultrasonic plane wave in which the particle motion is parallel to the wave vector and for which energy flow is parallel to the wave vector.
‘Rehabilitation aids for the blind’: disability and technological knowledge in Canada, 1947-1985
Published in History and Technology, 2020
One aspect of the work that still required sighted assistance, however, was the reading of a punched card. In early computing, a punched card contained the commands or data required to complete assignments. The programmer therefore needed to be able to interpret the information conveyed on the card in order to perform the work required of them.43 Although the American Printing House for the Blind had already developed a punched-card reader of this kind in the United States, the device was still not practical, ‘extremely tedious’ and difficult to read unless the location of the holes on the punch card were already known and only needed to be confirmed. Thus, largely due to requests from others in the blind community who were trying to establish themselves in the field of computing, Swail and his colleagues designed a machine that could enable programmers to quickly and easily read punch cards to complete their work.