The "6.0" in DECT 6.0 does not specify a spectrum band, but is a marketing term coined by Rick Krupka, Product Director with Siemens, for DECT devices manufactured for use in the U.S. and Canada. Although DECT 6.0 operates at 1.9 GHz, Rick decided the term DECT 1.9 might have confused customers who equate larger numbers (such as the 2.4 and 5.8 in existing 2.4 GHz and 5.8 GHz cordless telephones) with later products. The DECT and DECT 6.0 technologies are essentially identical, except for operating frequency.
DECT 6.0 products do not support "GAP", therefore phones of differing brands are not guaranteed to work together. E.g. A GE 28105EE1 DECT 6.0 headset will not receive calls if registered to a Uniden base unit.
The term DECT 6.0 is also used in Australia.
Read more about this topic: Digital Enhanced Cordless Telecommunications