If we look at the back of the unit we see only the hole for the fan exhaust and the power cable socket. Another difference between the the GS-1008 and the GS-1016 is that the GS-1016 has a power switch next to the power cable socket. It is a nice touch but you can mod a power cable with a switch or use a multi-plug with a switch for the same effect. It is important to have a way to switch off the unit though if it is in your bedroom because of the fan. It is good however that Zyxel included a power supply inside the unit. I have seen several rackmount units with a wall wart power supply. I think that wall warts should not be seen on professional equipment.
Above you can see the internals of the unit. The main circuit board, fan and power supply. There is nothing else.