3-1-2-1

Max Supply Voltage μC2 Exceeded

Beckhoff · EL1904 Digital Input Terminal

What does 3-1-2-1 mean?

The supply voltage to microcontroller 2 (μC2) within the EL1904 terminal has exceeded its maximum permissible limit. This overvoltage condition can stress internal components and potentially lead to permanent damage to the microcontroller.

Source: Beckhoff EL1904 Digital Input Terminal
Open Manual (Page 40)