The principle of Accurately Controlled Routinely Operated Signal System (ACROSS) is introduced in this paper. A sample machine is made and tested. The experiment shows that the signal stacking technique is effective in improving signal to noise ratio and the sompi cepstrum method is applicable to deconvolute a set of travel times of wave elements from accurate transfer function data in frequency domain. The principle of Accurately Controlled Routinely Operated Signal System (ACROSS) is introduced in this paper. A sample machine is made and tested. The experiment shows that the signal stacking technique is effective in improving signal to noise ratio and the sompi cepstrum method is applicable to deconvolute a set of travel times of wave elements from accurate transfer function data in frequency domain.