ACP/ARP
The azimuth of the radar for each return may be provided using a set of pulses called the ACP and ARP. The ACP (Azimuth Change Pulse) is a pulse train where the interval between pulses is a fixed angle. Commonly there are 2048, 4096 or 8192 pulses per 360 degrees. The ARP (Azimuth Reset Pulse) is a reset pulse that occurs at a reference point. The angle of the radar is therefore derived by counting the number of ACP pulses since the last ARP pulse.

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Note added at 18 mins (2009-05-01 16:52:40 GMT)
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BTW

you put "ACP/ACR" in the query

but I think you meant to put

ACP and ARP