some reorganization i propose to merge discrete time signal into this article and also the material in digital signal discussion that was recently split from discrete time signal by this will put description of the signal that results from sampling in context of the process that creates it covering discrete time signal comprehensively will result in a lot of unnecessary overlap with this article sampling signal processing removing digital signal discussion from that artcile will allow digital signal to be about one topic the pulse train signals used for digital logic digital signal is now part disambiguation and part article which is not good