January 2012 9.5 The Serial Interface of the Control 1767
Signal levels The levels of the individual signal lines differ:
 Data lines: The data signals are defined as being logical zero (SPACE) over 
the range +3 V to +15 V and logical one (MARK) over the range –3 V to –15 V.
 Control and verification lines: These signals are defined as being ON (High) 
over the range +3 V to +15 V and as OFF (Low) over the range –3 V to –15 V.
+ 15
+ 3
 3
 15
  0
LOW
OFF
"1"
MARK
HIGH
ON
"0"
SPACE
U [V]
Data signals Control and verification
signal
For all signals: The voltage range from –3 V to +3 V cannot be evaluated.