An illustration of the general 3-state chain with <i>per capita</i> transition rates <i>α</i>_<i>k</i> for <i>k</i> = 1, 2, 3, 4.

<p>State 3 (black) is the observable state (or open/conducting state) of the system, and all other states are not observable (or closed/non-conducting states). By convention, we identify <i>α</i>₁ ≡ <i>α</i>₁₂, <i>α</i>₂ ≡ <i>α</i>₂₁, <i>α</i>₃ ≡ <i>α</i>₂₃, and <i>α</i>₄ ≡ <i>α</i>₃₂.