Supriyono and Santoso, T. 2023. Four Digital Electronic Combination Key Using A 74HCT688 Comparator IC Accompanied with An Alarm as A Security. Best : Journal of Applied Electrical, Science and Technology. 5, 2 (Sep. 2023), 39–41. DOI:https://doi.org/10.36456/best.vol5.no2.7798.