A Guide to rpt.conf
In Asterisk configuration files "sections" are logical groupings of configuration information that begin with headings enclosed in brackets. For example,  begins and labels a section. Note that in some documentation the terms "context" and "stanza" are used in place of "section".
rxchannel This defines the name of the radio interface for the receive side of the radio node. For example, rxchannel=radio/usb. If there is no txchannel value defined in the node context then it is assumed that the same interface is used for transmit and receive.
txchannel This defines the name of the radio interface for the transmit side of the radio node. With the advent of full duplex interfaces this value is no longer used.
Node Directory Contexts