Truth value is a binary concept. Anything which has truth value must have one or the other of these values, and cannot have both. Our world is full of binary devices. Doors are either open or closed. Light bulbs are either on or off.
Magnetic poles are either positive or negative.
The binary states of these devices have long been used to convey information. A store manager can indicate that the store is open to customers by unlocking the door. By locking the door, she indicates that the store is closed to customers. One business used to indicate that it was open by turning on a red light. If the red light was off, the business was closed.