良好的数据库设计，可变数量的属性

I'm trying to create a database that contains a list of equipment. All of the equipment will have certain common attributes (such as manufacturer, model #, serial #, etc.), then there are other attributes that are specific to a certain piece of equipment (ie, a modem will have an access #, whereas a solar panel will have an output capacity). I'm not sure how to represent these changing attributes with good database design principles, I've tried searching the web, but I'm not entirely sure what to search for. I'm trying to create a database that contains a