24V is the most common signal level for the terminals, however, some also support other voltage levels, for instance 5V, or 12V or…. In that case, normally the terminal needs to be powered with the same voltage. For 5V terminals, normally a EL9505 is added before the 5v terminal in the ethercat chain supplying the power bus with 5V.
Example of slaves needing 5V power supply:
If a 5V terminal is supplied with 24V it will most likely break. Make sure the terminals has the correct power supply before powering the system.
The voltage level of the power bus after (downstream) of a 5V terminal is normally also 5V, if another voltage is needed then another system terminal is needed to set a new voltage level of the power bus