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.