The first letter of the three character channel code specifies the general sampling rate and the response band   
of the instrument.  (The "A" code is reserved for administrative functions   
such as miscellaneous state of health.)   
   
Band  codeBand type                       Sample rate (Hz)        Corner period (sec)   
F     ...                                 ≤ 1000 to < 5000        ≤ 10 sec   
G     ...                                 ≤ 1000 to < 5000        ≤ 10 sec   
D     ...                                 ≤ 250 to < 1000         ≤ 10 sec   
C     ...                                 ≤ 250 to < 1000         ≤ 10 sec   
E     Extremely Short Period              ≤ 80 to < 250           ≤ 10 sec   
S     Short Period                        ≤ 10 to < 80            < 10 sec   
H     High Broad Band                     ≤ 80 to < 250           ≤ 10 sec   
B     Broad Band                          ≤ 10 to < 80            ≤ 10 sec   
M     Mid Period                          < 1 to < 10   
L     Long Period                         ≈ 1   
V     Very Long Period                    ≈ 0.1   
U     Ultra Long Period                   ≈ 0.01   
R     Extremely Long Period               ≤ 0.0001 to < 0.001   
P     On the order of 0.1 to 1 day1       ≤ 0.00001 to < 0.0001   
T     On the order of 1 to 10 days        ≤ 0.000001 to < 0.00001   
Q     Greater than 10 days                < 0.000001   
A     Administrative Instrument Channel   variable                   NA   
O     Opaque Instrument Channel           variable                   NA