Intercept time is a key factor in the performance of electronic warfare (EW) surveillance and reconnaissance equipments. Interception relates to the probability of time coincidence of two or more parametric windows; scanning antennas, sweeping or stepping receivers and frequency-agile emitters give examples of such windows, where alignment or coincidence is required before detection can occur. Formulas summarised in the paper give a representative basis to the calculation of intercept time statistics, as well as allowing the duration of an intercept to be evaluated. Predicted results from computer modelling indicate that these new formulas give a much better representation of the intercept problem than that given in previous studies.