The CL660HX handset is a landline phone that uses an analogue connection, and it does not support DECT technology. TP-Link 4G LTE routers typically do not have DECT capabilities either. Therefore, this handset is not compatible with a TP-Link 4G LTE router in terms of DECT functionality. However, if you are looking to use a landline phone with a 4G LTE router, you might consider using an analog telephone adapter (ATA) to connect your analogue phone to a VoIP service via the router.