SXS consists of two gas proportional counters (SXS-1 and SXS-2) filled with xenon and carbon dioxide (1.16 atm) and has a beryllium window of 0.15 mm thickness. The field of view of each detector is 10 deg x 10 deg. Each of the two detectors covers the photon energy band from 3 keV to 40 keV. SXS-1 has a large effective area which is suitable for detection of small flares, whereas SXS-2 has a small effective area which is suitable for detection of large flares. The energy resolution is about 20 % at 5.9 keV and 12 % at 22 keV. The inflight energy calibration is achieved by detection of 5.9 keV line emitted by a Fe-55 radioactive source. Both SXS-1 and SXS-2 have two PC channels; PC11 and PC12 for SXS-1, and PC21 and PC22 for SXS-2. The first suffix denotes the counter and the latter suffix indicates the energy channels (low; 1 and high; 2). For example, PC12 is the higher energy band of SXS-1. The lower energy bands range from LD to MD1, while the higher energy bands range from MD1 to MD2. These discrimination levels (LD, MD1, and MD2) as well as the gains of the pulse counting electronics circuit (h) and the high tension levels (g) can be independently selected among the four-entry options, respectively.
The discrimination level (y=LD, MD1, and MD2) of the SXS PC channels can be obtained by the following relations.
y(keV) = a * (x +9)/h/g
SXS-1 : a = 0.30
h g LD(x) MD1(x) MD2(x)
00 1.00 1.00 0 40 103
01 0.67 1.36 0 58 127
10 1.47 1.75 0 74 127
11 2.24 2.75 0 91 127
SXS-2 : a = 0.28
h g LD(x) MD1(x) MD2(x)
00 1.00 1.00 0 36 94
01 0.66 1.47 0 54 127
10 1.47 1.87 0 69 127
11 2.15 3.02 0 85 127
The settings were all null (00) before June 18, 1992 and only the gains were changed to g = 01 (for SXS-1 and SXS-2) since then.
The total deadtime of these PC channels is 9 
s. The
correction factor is tabulated in the file $DIR_WBS_CAL/dtcorrf.dat.
Distortion of the energy versus pulse-height relationship in the PH mode was found after the launch, which might have resulted from the failure of the pulse-height-analysis electronics circuit. No reliable energy calibration for the PH data is available at the moment.