The appropriate product category
- The residual voltage is the voltage that remains in an output transistor while it is ON.
For example, consider an NPN output with a power supply voltage of 24 V and a residual voltage of 2 V. While the output transistor is ON, there will be 2 V between the output line (the black wire) and the 0-V line (the blue wire).
A relay, timer, or other load is connected between the power supply line (the brown wire) and the output line (the black wire).
A voltage of 22 V is applied to the load at this time.
(Voltage across the load of 22 V = Power supply voltage of 24 V - Residual voltage of 2 V)