KEYER_WITH_DOT_MEMORY

Published:2009/7/11 2:52:00 Author:May | From:SeekIC

Features include self-completing characters, exact timing of characters, and dot memory. Timing circuit uses 74121 mono MVBR U1, serving dot gen-erator and output stage U2A, dot memory U2B, and dash generator U3A-U3B. U2 and U3 are 7473 dual JK flip-flops. Length of timing pulse is iletermined by R1-G1, with R1 controlling speed of keyer. Pulse-width stability at all speeds is better than 5% between first and all following pulses. Dot memory U2B allows keying of dot at any time, even if dash has not yet been completed. Dot is held in memory and keyed out automatically after dash. Diodes are 1N914.-J. H. Fox, An Integrated Keyer/TR Switch, QST, Jan, 1975, p 15-20.



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