The standard decode tone is heard after the 1st decode and any odd numbered decode after that (3rd, 5th, 7th, etc.). A higher frequency “rescan beep” tone is heard after the 2nd decode and any even-numbered decode after that (2nd, 4th, 6th, etc.). If the standard decode tone is changed to something other than the default, the odd-numbered decodes would use this newly defined tone while the even-numbered decodes would always use the rescan beep tone.