Lyric Computer - The 4G680 supports extenal landline phones via VoLTE( Voice over LTE) or CSFB (Circuit Switch Fallback). Simply connect the landline phone to the phone port of the 4G680 and
Tenda 4G680V2.0 3G/4G 300Mbps Wireless N300 4G LTE and Volte Router (SIM Based, Not a Modem) : Amazon.in: Video Games
180131 Tenda 4G680 Datasheet
Tenda 4G680 300Mbps Wireless 4G LTE, VoLTE Router - YouTube
Discovery Info Center - Tenda 4G680 300Mbps Wireless N300 3G 4G LTE and VoLTE Router Tenda 4G680 Provides 4G LTE Mobile WAN and wired WAN connection to let you surf the internet