3M 965AMS User Manual

Since impulse hits, noise and other power related interference 

can fluctuate during the day you have the option of measuring 

three different levels. If you traditionally measure Impulse hits at 

a threshold of 40 dBrn, then select a count threshold of 32 and a 

spread of 2 dB, then you will be able to see any hits that exceed 

32, 36 or 40. Although this circuit will pass at 40, you will be 

able to see if there is noise just under the threshold that can 

appear later with a change in power usage or plant conditions.
Selected a spread of 4 dB and a threshold of 32 would allow you 

to count hits that exceed 32, 36 and 40.

Check with your DSLAM vendor regarding excessive hits for a 

circuit. Different DLSAM vendors have settings to make use of 

buffers (dynamic memory) to compensate for errors that can be 

caused by impulse noise.