Abstract: An interrupt generator comprising an optical coupler and a number of cascaded bidirectional one shots. The input of the optical coupler is coupled to AC powerlines which provide power to a computer. The output of the optical coupler is an isolated square wave signal having the same frequency as the AC powerline. This output is used to trigger the input of the first one shot in a string of one shots. The first one shot has an output which triggers the inputs of a second one shot, which, in turn, triggers the inputs of the third, etc. The one-shot outputs provide a series of even multiples of the AC powerline frequency each synchronized with the powerline. A selected output of one of the one shots is passed through a buffer to the computer as an indication of the optimum time to sample data in a real time data acquisition system.