Small Aircraft; High Wing; 1 Eng; Fixed Gear
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 2.7
Situational Awareness; Distraction; Human-Machine Interface
ATC Issue All Types; Conflict NMAC; Deviation / Discrepancy - Procedural Other / Unknown
Air Traffic Control Issued New Clearance; Air Traffic Control Separated Traffic
ATC Equipment / Nav Facility / Buildings
Aircraft X was tracking the localizer back course in ZZZ at 2300 feet. Aircraft Y departed ZZZ1 southwest bound and climbing. Collision alert activated and I attempted to move Aircraft X's datablock to be able to see conflicting traffic. I was unable to move the datablock. I then attempted to disable auto offset and input the wrong entry. After correctly disabling auto offset I moved Aircraft X's datablock; located the conflicting traffic; and issued a traffic alert. Aircraft X's target merged with the conflicting traffic at the same altitude. Aircraft X stated over the frequency 'That was really close.' Aircraft Y then called for services and was radar identified and altitude verified. The restriction of datablocks while in collision alert and auto offset enabled is unsafe and will; potentially; lead to the loss of life during time critical safety situations. Remove the restriction limiting controllers from manipulating datablock position while auto offset is on and a datablock is in collision alert.
NCT TRACON Controller reported when two aircraft activated Conflict Alert on their radar display they were unable to separate the overlapped data blocks to issue appropriate control instructions and a Traffic Alert.