The paper describes a method of measuring correlation functions of binary time signals. The use and application of correlation functions are discussed in a general manner, and the authors point out the diversity of fields in which these functions are found. A method of correlation employing logic switching devices is detailed, and, as an example of operation, the autocorrelation of binary noise which has zero crossings occurring at random intervals is described. Finally it is shown that the method is satisfactory and has certain advantages.