BS EN ISO 07200-2004

Technical product documentation — 

Data fields in title blocks and document headers

https://drive.google.com/open?id=1nHijxNKKq7PxI3kleNFzJbSNRQ7nowDc

5.2.4 Sequence of letter codes for control functions

L e t t e r  c o d e s  f o r  c o n t r o l  f u nc t i o n  s h a l l  b e  r e p r e s e n t e d  i n  f o l l o w i n g  s e q u e nc e :  I ,  R ,  C ,  S ,  M ,  Z ,  a n d  A ,  f o r  e x a mp l e :

—  ICA Indication, control (closed loop) and alarm;

—  CS Control (closed loop) and switching (open loop);

—  ICZA Indication, control (closed loop), switching (open loop) safet y relevant, and alarm.