Complex sentence: The DECT standard fully specifies a means for a portable unit such as a cordless telephone to access a fixed telecoms network via radio, but unlike the GSM standards does not specify any internal aspects of the fixed network itself.
Split into simpler sentences: The DECT standard fully specifies a means for a portable unit, such as a cordless telephone, to access a fixed telecoms network via radio. But, unlike the GSM standards, does not specify any internal aspects of the fixed network itself.