If you don't know it, you won't be able to automate your Wifi Protected Setup (WPS). The pin is a very specific way to prevent yourself from always having to remember codes, keys, passphrases, etc. Without it, its like saying that you want to to connect to Bank of America, and that it's just okay because you want it to happen.
The following is taken from the
ESR-9753 manual:- Wi-Fi Protected Setup (WPS)
WPS is the simplest way to establish a connection between the wireless clients
and the wireless router. You don’t have to select the encryption mode and fill in a
long encryption passphrase every time when you try to setup a wireless
connection. You only need to press a button on both wireless client and wireless
router, and the WPS will do the rest for you.
The wireless router supports two types of WPS: WPS via Push Button and
WPS via PIN code. If you want to use the Push Button, you have to push a
specific button on the wireless client or in the utility of the wireless client to start
the WPS mode, and switch the wireless router to WPS mode. You can simply
push the WPS button of the wireless router, or click the ‘Start to Process’ button
in the web configuration interface. If you want to use the PIN code, you have to
know the PIN code of the wireless client and switch it to WPS mode, then fill-in
the PIN code of the wireless client through the web configuration interface of the
wireless router.
