Siemens Simatic RTU303xC Series Operating Instructions Manual page 52

LEDs, connectors, buttons, card slots
2.3 Interfaces and connectors
You configure the power supply of the RTU itself and the control outputs of the RTU in the
WBM, refer to the section Power supply (Page 171).
Note
Output voltage
The voltage at the terminals X10, X11, X40 and X42 of the RTU and CTRL at the extension
board can be set to 12 or 24 V DC in the WBM for all control outputs.
Maximum cable lengths:
The maximum length of all cables connected to the RTU or the extension board is 30 m.
Design of the connectors as plug-in terminals
The connectors are designed as plug-in screw terminals located side by side on the top and
bottom of the device. By removing the terminals you can wire the individual connectors even
when there is little space and then plug them in again even if the device is already in a
protective housing.
Reverse polarity protection
All terminals are designed so that they can only be plugged into one position. This provides
constructional reverse polarity protection.
The connector X10 IN to the external power supply of the RTU also has electronic reverse
polarity protection.
X10: Voltage input of the RTU and control output for actuators and sensors
X10 is a connector with a 5-pin terminal.
● X10 IN
The RTU is supplied with an external voltage via the connector X10 IN. Voltage sources
with a voltage range of 12 to 24 VDC are possible.
If you operate the device in a control cabinet, you can use a power supply that does not
comply with NEC Class 2. When connecting up the device, adhere to the safety notices
listed below.
52
WARNING
Safety extra low voltage
The device is designed for operation with a directly connectable safety extra-low voltage
(SELV) according to UL/IEC 61010-1 and UL/IEC 61010-2-201 whose output power
corresponds to "Limited Energy" according to UL/IEC 61010-1.
Operating Instructions, 06/2019, C79000-G8976-C382-06
RTU303xC