Yastar TG400L GSM Gateway is a device used to convert the GSM mobile sim into a phone line that is compatible with PABX devices for sending and receiving, as it is an ideal solution in the absence of landlines. Features of Yastar TG400L GSM Gateway LTE VoIP Gateway - 4 x LTE Port - 2 x 10/100 Ether Port - Voice Codec: G.711 A/u-law, G.726, G.729 A, GSM, Speex