Abstract: The time-compressed correlator has been widely applied in matched filter of active sonar since 1960's. The principles of DELTIC and MACORMATIC can not be directely used in passive sonar due to the limitation of sampling frequency and data length. Otherwise the input data will be missed periodically in the system output. An Alternative Access Time-compressed Correlator (ALATIC) is proposed in this paper, by using a buffer register the correlation operation of arbitrary length can be done in real time. This model is a general purpuse correlator, which can be used in both active and passive sonar. The running positive order and inverse order register and the shift positive order and inverse order model are presented. The hardware implementation and the flow chart graph of ALATIC is also described. The model presented in this paper can be used in digital sonar design.