Garmin GNC 255, Installation Manual, Page: 88 / 138

GTR 225/GNC 255 TSO Installation Manual 190-01182-02
Page B-8 Rev. B
B.2.4.1.3 Set Standby COM Frequency and Transceiver Function.
This message is used to set the standby COM frequency as well as the COM transceiver function.
Message format:
“C” ..........................Message class. This is a GTR/GNC COM message.
“01”.........................Message identifier.
mk ...........................Standby COMM frequency:
m = desired frequency in MHz in hexadecimal, where m = desired frequency -
30h, with desired frequency in range of 118 to 136MHz.
k = desired frequency in KHz, where k = (desired frequency / 25 KHz) + 30h,
with desired frequency in range of 000 to 975KHz in 25KHz steps.
a...............................Transceiver function: N = normal, M = monitor, 0 = unchanged.
o ..............................8.33 KHz offset: (ASCII) 0 = 25 KHz frequency (.000); 1 = first 8.33 KHz
channel offset (.005); 2 = second 8.33 KHz channel offset (.010); 3 = third
8.33 KHz channel offset (.015)
Example messages:
$PGRMC01KFM2<chksm><CR><LF>
This example command would set the standby COM frequency to 123.565MHz and place the COMM
radio in Monitor mode. This is interpreted by noting that the ASCII ‘G’ corresponds with 47h, +30h = 77h,
converted to decimal equals 119 for the MHz portion. The KHz portion converts ASCII ‘F’ to 46h, -30h
yields 16h, x25KHz steps = 550KHz , add 3 8.33 channels = 565KHz.
Note: The GTR/GNC will check input frequencies for validity. An RS-232 serial error message output will
be generated if the frequency is invalid, or an 8.33 KHz frequency is requested when the GTR/GNC is in
25 KHz channel spacing mode.
B.2.4.1.4 Set COM Volume Level and Audio Control Parameters
This input is used to set the volume level for the headphone output, and various audio controls parameters.
Message format:
“C” ..........................Message class. This is a GTR/GNC COM message.
“02”.........................Message ident.
n ..............................Data type: (ASCII) 1 = headphone, 4 = sidetone level, 9 = RF squelch
vv ............................Volume level: 00-FFh; two encoded hex characters (30h-3Fh).
Example message:
$PGRMC0211=<chksm><CR><LF>
Set the speaker output volume to 1Dh out of FFh (“=“ = 3Dh, -30h = Dh).