User Guide
Page 39
... P-662HW-D1, denote a device that works over T-ISDN (UR-2). 1 Only use firmware for your ZyXEL Device's specific model. Models ending in this guide pertain to remote networks. Models ending in "3" denote a device that works over the analog telephone system, POTS (Plain Old Telephone Service). Refer to the label on the bottom of the ZyXEL Device. P-662H...
... P-662HW-D1, denote a device that works over T-ISDN (UR-2). 1 Only use firmware for your ZyXEL Device's specific model. Models ending in this guide pertain to remote networks. Models ending in "3" denote a device that works over the analog telephone system, POTS (Plain Old Telephone Service). Refer to the label on the bottom of the ZyXEL Device. P-662H...