Digital signals have two states or interger values
You are mixing up the ideas of digital signals with binary signals.

A digital signal is one that takes only discrete values, or, in the real world, one in which we distinguish only a discrete set of values. It might have 2 possible values, or 3, or 10, or whatever.

A binary signal is a specific case of a digital signal that takes two different values. 

A ternary digital signal can take three different values.

In communications, we often use complex modulation schemes that can take one of many different values in each baud interval. For example, quadrature amplitude modulated (QAM) systems might allow 16, 64, 256, or more different values.

A clock can have a digital display without any binary logic being involved in its design:


(image source: theclockgallery.com)