Sardinas and Patterson gave a polynomial-time algorithm to determine whether the extension of one of these constructs is non-singular, in which case a result of McMillan shows that one of these constructs satisfies Kraft’s inequality. A method to produce these constructs by iteratively partitioning elements of the source into two sets of approximately equal probability was given by (*) Fano. That method always attains a mean length within one bit of the lower bound established by Shannon’s theorem named for the “noiseless” type of these constructs, which for a binary one of these constructs is given by (-5[1])the entropy of the underlying information source. These constructs are automatically prefix-free when their namesake (-5[1])“words” all have the same length. For 10 points, name these systems used in telecoms, one of which is named after Samuel Morse. ■END■ (10[3])