Siemens Simatic S7-400 - Manual (Page 172)

Digital Modules
4-50
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
4.13 Digital Input Module SM 421; DI 16 120/230 VUC;
(6ES7 421-1FH00-0AA0)
Characteristics
The SM 421; DI 16 120/230 VUC is characterized by the following features:
• 16 inputs, isolated
• Rated input voltage 120/230 VAC/VDC
• Suitable for switches and two-wire proximity switches