NS Discovery will find out network Printer during discovery, what's the way/criteria that NS will know it is a printer?

HI all,

I have a All-in-One Altiris Notification Server 7.1 (Virtual Machine) for PC inventory & software deployment with MSSQL database 2008 R2.

1) NS Discovery will find out network Printer during discovery, what's the way/criteria that NS will know it is a printer? Thanks.

2) How about network switch?what's the way/criteria that NS will know it is a network switch? Thanks

Thanks