Siemens Simatic S7-400 - Manual (Page 142)

Digital Modules
4-20
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
4.8 Digital Input Module SM 421; DI 32 24 VDC;
(6ES7421-1BL01-0AA0)
Characteristics
The digital input module SM 421; DI 32 24 VDC has the following features:
• 32 inputs, isolated in a group of 32
• 24 VDC rated input voltage
• Suitable for switches and two/three/four-wire proximity switches (BEROs,
IEC 61131; type 1)
The status LEDs indicate the process status.
Notice
If you use the module with the order number 6ES7421-1BL01-0AA0 as a
replacement for the module with the order number 6ES7421-1BL00-0AA0, you can
leave PIN 3 wired. If you run modules 6ES7421-1BL00-0AA0 and
6ES7421-1BL01-0AA0 involved in mutual exchange, you have to wire and supply
PIN 3 as described in Section 4.7.