In program softwares like CHIRP and others, there are 4 or 5 different choices for the Tone Mode column. 2 of them are called "Tone" and "T Sql" which I assume stands for "Tone Squelch". What is the difference and how do you know when to use each one. I think the other choices are for digital radios or something like that which I'm assuming I don't need so I'm basically concerned with the aforementioned 2 items for tone. Can anyone educate me on this?