Technical Terms

p>Common in electrical wiring to share the terminals in multiple circuits.

Common wires are commonly used to simplify wiring.
They effectively reduce the number of terminals and the amount of cables. It also improves the circuitry and makes wiring easier.

On the other hand, such multiple circuits using common wires have more impact on the circuits because they share the common wires in case of failures such as disconnection or poor connection on the common wiring parts.
Accordingly, a stand-alone circuit used for the vital purpose could be adopted instead of the multiple circuits with common wires.

As for a DC circuit based on 24V, the common wires are called "Positive common" or "Negative common".
The positive common indicates the wiring on the voltage supply side, and the negative one shows the 0V side. For safety in case of disconnection, the positive common is mainly adapted.

In common wiring, terminal blocks are mainly used to connect.
In some cases, PLCs and other devices have internal, commonly wired circuits and common terminals.
Common wiring is not used for grounding.
For reference, you can see the similar words of "Common mode" and "Common mode noise," where the direction of the noise currents on the positive and the negative sides of the power supply have the same direction.

Common | Technical Terms: Power Supplies | Matsusada Precision