13th March 2006 - Full PDF Text Version
To allow for call transfer notification on analog phones, an alternate dial tone (also known as interrupted, broken, or stutter dial tone) will be heard after pressing the flash/recall button or after pressing the on-hook button quickly. This tone distinguishes between a user attempting to transfer a call and a user ending a previous call and going off-hook to make a new call. This feature is available in V2.1, and V3.1 and subsequent software versions.
Alternate dial tone specifications:
Frequency: same as the standard dial tone for the specific locale.
Cadence: locale specific - 0.25 seconds on, 0.25 seconds off for enu locale.
Please note that for some locales standard dial tone is cadenced.