Yes, although you can also use GSM or SIP and it's often called a DECT number even if you're actually on one of the newer networks, since the number space is th

Yes, although you can also use GSM or SIP and it's often called a DECT number even if you're actually on one of the newer networks, since the number space is the same. DECT simply was there first and thus became the generic term for the internal phone network.