TE VoIP E1/ T1 /J1 gateway (VoIP to E1/T1/J1, and E1/T1/J1 to VoIP) supports up to 30/60 concurrent calls. TE Series offers SMBs cost effective additions to a legacy telephone system to bring the true benefits of VoIP. Yeastar ISDN VoIP Gateways bridge the gap between traditional ISDN telephony connections such as common RJ-48c / T1 interfaces to provide dial tone to most VoIP PBX phone systems.