Narrative:

Aircraft X eastbound at 35;000 feet; aircraft Y westbound at 35;000 feet. This area does not have an atop probe but has been identified to have a high probability of having this type of event happen due to crossing situations with all altitudes being used both east and westbound. The conflict alert identified an opposite direction conflict in the vicinity of [fix]. The controller attempted to descend aircraft X who was not on frequency because the aircraft was on a frequency which would have been the correct frequency 1 hour prior. After some time had elapsed aircraft Y was issued an immediate climb to 36;000 feet and appeared to be leveling as they passed. The aircraft did not have an RA event but did have a loss of separation. In my opinion there are 3 distinct holes in the swiss cheese theory which contributed to this event taking place and/or not being resolved immediately. Actually; I feel there are more than 3 but these 3 stand out in this situation. An audible conflict alert (ca) alarm is needed; the ca needs to be fixed in order to not give so many false conflicts; and there needs to be a probe in the snp radar volume.after watching the playback it was observed that the controller was not even aware there was a ca occurring when it was first displayed. It has been brought to management's attention on several occasions that the audible alarm is disabled. A considerable amount of time is spent on the secondary monitor which displays many other functions; all of which are time spent looking away from the display which is the only indication when a ca event is occurring. Without an audible alert; there are many occasions in performing normal duties in which a ca could go undetected and the controller not even aware it is happening.once the ca was observed it was not taken seriously and was thought to be just another erroneous indication. I feel this is because controllers have been desensitized to ca events due to the fact it regularly goes off because of false alarms. The causes are usually the aircraft unpairing and conflicting with itself; or showing a conflict when 1 aircraft is directly above another and the software can't differentiate the mode C; the 2 aircraft swap altitudes and conflict. (The 2nd of these occurs often enough that if 1 of these 2 aircraft at the same location; 1 above the other; is indeed in conflict with the other; a traffic alert would almost certainly never be issued)there needs to be a probe within the radar volume. It is not as simple as turning on the probe within this area; we recently tried this as a test and the amount of conflictions (which were being radar separated) was overwhelming and distracting to the point of having to turn it back off. There have been many proposals to fix the problems which are keeping it from being a simple fix of turning on the probe; none of which has been pushed to being a high priority. It took a near midair in another radar site area to bring enough attention to get things fixed; I'm unsure what type of event it will take for this safety issue to be taken seriously enough to move the atop program trouble reports (ptrs) to a higher priority but I hope it doesn't take the same. There have been numerous close calls over the years and many more that have been separated with pure luck vs positive control. I feel controllers do an excellent job and are vigilant at separating traffic without the probe in this area; however; this is an extremely congested crossing area with all altitudes in all directions and the human error factor is bound to kick in now and again.

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Original NASA ASRS Text

Title: The Controller was working two aircraft on converging courses at 35;000 feet. The Controller attempted to descend one of the aircraft but could not because it was on the wrong frequency. The Controller climbed the other aircraft; but not before a loss of required separation occurred.

Narrative: Aircraft X eastbound at 35;000 feet; Aircraft Y westbound at 35;000 feet. This area does not have an ATOP probe but has been identified to have a high probability of having this type of event happen due to crossing situations with all altitudes being used both east and westbound. The Conflict Alert identified an opposite direction conflict in the vicinity of [fix]. The controller attempted to descend Aircraft X who was not on frequency because the aircraft was on a frequency which would have been the correct frequency 1 hour prior. After some time had elapsed Aircraft Y was issued an immediate climb to 36;000 feet and appeared to be leveling as they passed. The aircraft did not have an RA event but did have a loss of separation. In my opinion there are 3 distinct holes in the swiss cheese theory which contributed to this event taking place and/or not being resolved immediately. Actually; I feel there are more than 3 but these 3 stand out in this situation. An audible Conflict Alert (CA) alarm is needed; the CA needs to be fixed in order to not give so many false conflicts; and there needs to be a probe in the SNP radar volume.After watching the playback it was observed that the controller was not even aware there was a CA occurring when it was first displayed. It has been brought to management's attention on several occasions that the audible alarm is disabled. A considerable amount of time is spent on the secondary monitor which displays many other functions; all of which are time spent looking away from the Display which is the only indication when a CA event is occurring. Without an audible alert; there are many occasions in performing normal duties in which a CA could go undetected and the controller not even aware it is happening.Once the CA was observed it was not taken seriously and was thought to be just another erroneous indication. I feel this is because controllers have been desensitized to CA events due to the fact it regularly goes off because of false alarms. The causes are usually the aircraft unpairing and conflicting with itself; or showing a conflict when 1 aircraft is directly above another and the software can't differentiate the Mode C; the 2 aircraft swap altitudes and conflict. (The 2nd of these occurs often enough that if 1 of these 2 aircraft at the same location; 1 above the other; is indeed in conflict with the other; a traffic alert would almost certainly never be issued)There needs to be a probe within the radar volume. It is not as simple as turning on the probe within this area; we recently tried this as a test and the amount of conflictions (which were being radar separated) was overwhelming and distracting to the point of having to turn it back off. There have been many proposals to fix the problems which are keeping it from being a simple fix of turning on the probe; none of which has been pushed to being a high priority. It took a near midair in another radar site area to bring enough attention to get things fixed; I'm unsure what type of event it will take for this safety issue to be taken seriously enough to move the ATOP Program Trouble Reports (PTRs) to a higher priority but I hope it doesn't take the same. There have been numerous close calls over the years and many more that have been separated with pure luck vs positive control. I feel controllers do an excellent job and are vigilant at separating traffic without the probe in this area; however; this is an extremely congested crossing area with all altitudes in all directions and the human error factor is bound to kick in now and again.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.