User Guide
Page 38
... Models with "3" as the next to the last character (like the P-2602HWL-D3A) denote a device that works over ISDN (Integrated Services Digital Network). Note: Only use firmware for each standard are from your ZyXEL Device's specific model. Refer to detect the speed of your device's key...is compatible with "1" or "7" as the next to remote networks. The ZyXEL Device is ideal for high-speed Internet browsing and making LAN-to-LAN connections to the last character (like the P-2602HWL-D1A or the P-2602HWL-D7A) denote a device that works over T-ISDN (UR-2). Models with the...
... Models with "3" as the next to the last character (like the P-2602HWL-D3A) denote a device that works over ISDN (Integrated Services Digital Network). Note: Only use firmware for each standard are from your ZyXEL Device's specific model. Refer to detect the speed of your device's key...is compatible with "1" or "7" as the next to remote networks. The ZyXEL Device is ideal for high-speed Internet browsing and making LAN-to-LAN connections to the last character (like the P-2602HWL-D1A or the P-2602HWL-D7A) denote a device that works over T-ISDN (UR-2). Models with the...