64th Air Division personnel were assigned to main stations of the 1957 DEW Line and annually inspected auxiliary/intermediate DEW stations maintained by the "DEW M&O Contractor" (the White Alice Communications System linked ADC aircraft with DEW Line radars.) On 1 March 1957 CONAD reduced the number of ADC interceptor squadrons on alert for the Air Defense Identification Zone. "At the end of 1957, ADC operated 182 radar stations…32 had been added during the last half of the year as low-altitude, unmanned gap-filler radars. The total consisted of 47 gap-filler stations, 75 Permanent System radars, 39 semimobile radars, 19 Pinetree stations,…1 ] radar and a single Texas Tower". ADC subsequently became a CONAD component of NORAD, for which the international agreement was signed on 12 May 1958 (RCAF officers agreed NORAD's "primary purpose would be…early warning and defense for SAC's retaliatory forces.")