Siemens SIMATIC NET S7-1200 Compact Operating Instructions

5.1 Possible sources of problems and how to deal with them
Fuses
Note
The CSM 1277 compact switch module has a resettable fuse / PTC. If the fuse triggers (all LEDs
are o󹪜 despite correctly applied power supply), the device should be disconnected from the
power supply for approximately 30 minutes before turning it on again.
LED display when voltage is too low
If the power supply is too low, then the internal power supply will switch o󹪜 causing the DIAG-
LED and all port LEDs to go o󹪜. The functionality of the CSM 1277 is no longer available. A supply
voltage of at least 19.2 V is necessary for correct operation.
LED display in case of reverse polarity of the power supply
The CSM 1277 is equipped with reverse polarity protection. A reverse polarity of the supply
voltage does not cause any damage but will not result in any function either. The DIAG‑LED and
all port LEDs are o󹪜.
Device defective
If a fault develops, please send the device to your SIEMENS service center for repair. Repairs on-
site are not possible.
Maintenance and troubleshooting
5.1 Possible sources of problems and how to deal with them
Compact Switch Module CSM 1277
38 Compact Operating Instructions, 06/2022, A2B00079397-02

Siemens SIMATIC NET S7-1200 Specifications

General

Supply voltage	24 V DC
Protection class	IP20
Product type designation	S7-1200
Transfer rate	10/100 Mbit/s
Number of ports	4
Power consumption	2.5 W
Operating temperature	0 °C to 60 °C
Mounting type	DIN rail
Switching capacity	1 Gbps