In the beginning, having very little in the way of physical resources, Iida had no choice but to tap external sources. In addition to domestically produced sensors, foreign-made sensors were also used in the early stages of the development of the SP Alarm System. Ademco sensors, imported from the United States until 1969, were used to detect the opening of doors and windows. Sensors for safes were purchased from the British firm, Securitas, until 1971. With both products delivery was difficult to coordinate and there were problems with post-installation maintenance.