Have you tried selecting a different tone on the phones to get a less annoying ring and to see if all end up with the "beeps" afterward? Is it just tone 2, or all of them?

More importantly, I think what you are actually looking to change is the incoming line ring tone.
One of four different ringing tones can be selected for each line in Class 11.31.


"I'm the one that has to die when it's time for me to die, so let me live my life, the way I want to."
-- Jimi Hendrix