Some models of fax boards can support up to 46 channels, with two boards supporting 23 channels each, and so the process of finding the correct hexadecimal number can be complex. Here is a simple example of how to turn inbound channels on and off for an eight channel fax board. For an eight channel board, the channel layout equates to an eight-digit binary number, with channel 1 represented by the rightmost digit. Therefore, enabling channel 8 equates to 1000,0000 as a binary value. The equivalent hexadecimal number for 1000,0000 is 80. Thus, you would set enabled.channels to 80.
Likewise, if you wanted to enable channels 7 and 8 as outbound (binary 1100,0000 or hex C0), you would set outbound.enabled.channels to C0.
A 23 channel fax board requires 23 binary digits (channels 0 through 22). If you wanted to enable channels 15 through 22 as outbound channels, this would equate to 111,1111,1000,0000,0000,0000 as a binary value, which corresponds to hex 7F8000. So to enable outbound channels 15 through 22, set outbound.enabled.channels to 7F8000.