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The correspondence between the PROS 34-channel spectra and PI bins
is listed in
Tab. 3.3.
The PI bins,
256 channels, are 10eV wide, with the low energy given by
eV (by the inherent nature of
proportional counters, this is not an exact relation and should only
be considered in a statistical sense).
The lower level discriminator is set in ADC channel 7,
for the observations before 1991 October,
and ADC channel 10-11 for those thereafter.
To be conservative, in the 256 channel scheme,
for data taken before 1991 October 14 channels 1-8
and channels above 
200 should be ignored.
For data taken since 1991 October 14
channels 1-10 and channels above 
should be ignored.
The upper limit is a loose one, as the effective area calibration
gets gradually worse between 2 - 2.5keV.
We do not recommend using data above 
keV at this time.
The counts detected in channels 260-370 are due almost entirely to
the particle background. PROS will display these events,
by specifying the desired range in PI channels.