Touchstone&reg; Telephony Modem TM502A Based on the success of the Touchstone TM402 product family, ARRIS introduces the Touchstone Telephony Modem TM502A. The Touchstone Telephony Modem TM502A delivers two lines of primary line Voice over IP (VoIP) along with High-Speed Data Access DOCSIS 2.0 based and PacketCable 1.0 complaint design provides a solution for the long-term