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Siemens  TX-I/O™ Module system – Functions and operation  CM110561en_08 
Building Technologies  Default functions, disabling function  2018-10-25 
Testing options with default functions 
 
TXM1.8D, 16D  (BI Default) 
 
   
TXM1.8U (-ML), TXM1.8X (-ML)
 (UIO Default) 
 
 
No voltage 
(input open or shorted) 
OFF 
 
 
–75 ... +75 µA  at input  OFF 
High-resistance 
conductivity tester   
 
 Do not use! 
 
>75 µA at input  ON 
 
Correct polarity of  
low-resistance 
conductivity tester  
  < –75 µA at input  Flashing 1 Hz 
 
Incorrect polarity of  
low-resistance 
conductivity tester  
  >11.5 V at input  Flashing 1 Hz 
E.g. DC24 V connec-
ted by mistake  
  AC24 V at input  Flashing 1 Hz 
AC24 V connected by 
mistake  
(no LCD)  Especially short circuit 
  > 40 Ohm at input  OFF 
(no LCD)   
TXM1.6R (-M), TXM1.6RL, TXM1.8T (BO Default) 
digital outputs 
Local override or tool 
override enabled  
ON / OFF 
The module executes all local over-
rides or tool overrides directly, without 
safety precautions or interlocks.  
 Special care is required 
 
Testing of 
analog outputs 
TXM1.8U (-ML),  
TXM1.8X (-ML) 
UIO Default is an input function. For safety reasons, 
planned analog outputs can not be tested with 
unconfigured modules.  
As soon as the modules are configured, you can use the 
functional tests of the building automation and control