6-11 Safe Torque Off 
AC30V series Variable Speed Drive 
TRUTH TABLE 
 
Overview 
STO Input A 
X10/01 
STO Input B 
X10/03 
Drive Function 
STO Status Output 
X10/05, X10/06 
STO Active 
0V  0V 
Drive cannot start or supply power to its motor. STO trip 
reported.  
This is the intended safe state of the product with correct 
dual-channel operation. 
ON 
Abnormal one-
channel 
operation 
detection 
24V  0V 
Drive cannot start or supply power to its motor. STO trip 
reported. If either of these conditions persists for more than 
3.0 seconds (the maximum fault detection time), the STO 
function will lock into a fault state. The drive cannot start until 
the fault is rectified; all power is removed and reapplied (both 
mains and any auxiliary 24V dc power). 
This is single channel operation and thus deemed not as 
intended for category 3 / PLe / SIL3 structure 
implementation. 
OFF 
0V  24V 
STO Inactive 
24V  24V 
Drive is enabled to run under software control. The drive can 
supply power to its motor. 
OFF 
unpowered 
Don’t care  Don’t care  Drive cannot start or supply power to its motor.  OFF