From NAS-Central Zyxel Wiki
The reset button has 3 functions:
- Reset admin password and ip address
Press it for about 3 seconds until the first beep.
- Open a telnet backdoor
Press it for about 8 seconds until the second beep
- Reset to factory defaults (data on disk(s) remain untouched)
Press it for about 16 seconds. (8 seconds after the second beep)