Yes, you are indeed correct! I merely copied the portion of the page 85 referring to how to reset to the factory defaults. There are several other pages in the corresponding chapter, which include other pertinent details.
Chapter 36.2 of Reference Manual is also cited:
BOOTP/TFTP Firmware Recovery of the Network Module
The network modules use BOOTP/TFTP for firmware recovery through their built-in BOOTP/TFTP client when the network modules are restarted. To recover the firmware, first download it from the ZyXEL web site and store it on your computer. You can use any BOOTP/TFTP server (for example, BootpTftp.exe) to update the network module's firmware. The update procedure for BootpTftp.exe is as follows:
Do not turn off the IES-1000 during the updating process, as it may corrupt the firmware
1. Connect your network module's LAN port to a computer's LAN port directly using a crossover Ethernet cable, or connect both to an Ethernet hub/switch using straight-through cables.
2. Connect your network module's console port to a computer's serial port with a console cable.
3. Run any terminal emulation program, for example, Windows' built-in HyperTerminal, with the following parameters:
VT100 terminal emulation
No parity, 8 data bits, 1 stop bit
No flow control