Matrix feature-rich ATAs offer connectivity to VoIP, GSM and POTS networks. An ATA user can plug standard analog telephone devices to the ATA and the analog device(s) will connect transparently to the IP and GSM networks. An ATA thus provides a user with the ease of using a standard telephone instrument, yet make VoIP and GSM calls. The ATAs can also be interfaced to existing PBX system, offering GSM and IP line to be shared among the PBX users.