Welcome to the world of ALE.
[2021-10-25 21:56:41 4239.50] [Sounding THIS WAS] [From: XSS] [His BER: 20]
THIS WAS -> is usually abbreviated as
TWS. This is the call sign (C/S) of the station that
was transmitting. In you log, TWS is XSS. You will see a TWS at the end of a sounding or at the end of a transmission during the "unlink" process.
When stations are "talking" to each other, you will get a
THIS IS (TIS) followed by the call sign. For example:
[20:22:27][FRQ 13446000][TO ][MP9FEM ][TIS][WA0FEM ][AL0] BER 26 SN 03
translates to C/S WA0FEM to C/S MP9FEM. Both of these are FEMA stations.
The duration of a soundings is determined by how many channels is in the net. 2G is simply
2nd generation (AUTOLINK II).
If you are lucky you can catch an AMD - Automatic Message Display (designed to be a circuit engineering message). This is a short text sent from one station to another. Here is an example:
[00:10:50][FRQ 69131000][TO ][GNOC1 ][TIS][GMC225 ][AL0] BER 30 SN 13 [AMD]DAY TWO UNDERWAY. NOTHING TO REPORT.
Here is a quick primer for you:
http://www.milspec.ca/modems/ale.html