High-precision frequency and time standards are becoming more and more widely used in many technical fields. The basic equipment used by the Central Radio Propagation Laboratory of the National Bureau of Standards in providing and broadcasting standard frequency and time signals is discussed. Mention is made of the manner in which it is adjusted and the corrections which may be applied to make use of the ultimate accuracy that may be expected in using these signals for measuring and calibrating similar equipment. Several methods are given for checking the frequency of precision oscillators and precision clock performance. Suggestions are given as to methods of recording and evaluating performance data for such standards. Expected improvements in constancy and accuracy and possible future changes in the types of standards used in physical time measurements are considered.