MSK - MSK Receiver Interface (for DGPS Beacon Receivers)
       1     2  3   4  5 6
       |     |  |   |  | |
$--MSK,xxx.x,xx,xxx,xx,N*hh<CR><LF>

Field Number: 
1) Frequency in kHz (283.5 to 325.0)
2) Frequency Selection
    M1 = Manual
    A1 = Automatic (field 1 empty)
3) MSK bit rate (100 or 200)
4) Bit Rate Selection
    M2 = Manual
    A2 = Automatic (field 3 empty)
5) Period of output of performance status message, 0 to 100 seconds ($CRMSS)
6) Checksum