Behavior on power cut and power return of the TBX IP20 modules
(Original Document)
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General
The following diagram describes the behavior on power cut and power return of the TBX IP20 modules. 
Tc
Time duration of power cut to power supplies (voltage < 14 V). 
Tr
Time duration of power return to power supplies (voltage > 19.2 V).
WARNING
UNEXPECTED SYSTEM BEHAVIOR
In order to ensure correct operation of an extension module on power cut and power return, it must have the same SV power supply as its base module. If this is not the case: a 24 V SV base and a 48 V extension (or vice versa) correct operation on power cut and power return is not assured.
Failure to follow these instructions can result in death, serious injury, or equipment damage.
SV module power supply voltage
If the power cut to the modules is less than 10 ms, it will not cause a fault in the module.
A break greater than 10 ms can cause the module to stop and therefore reconfigure on return of power.
The voltage supplied to the module is not monitored by the TBX.
IS sensors power supply voltage
If the power cut to the modules is greater than 2 ms, the voltage monitoring system detects this fault before the fastest input is set to 0, (except for the TBX DES 16F22 module that has an input filtering time of 1 ms).
Similarly, when the supply voltage exceeds 19.2 V, the voltage monitoring system waits for 16 ms before signaling this, so as to be able to set the slowest input (except for modules that have an input wiring check whose filtering time is 35 ms).
This combination enables the coherence of input values to be assured, when no power supply fault to the sensors is signaled.
A break in the power supply to the sensors will not cause any internal fault to the module.
OS preactuators power supply voltage
If power to the preactuators is cut for more than 1 ms, voltage monitoring detects this fault and sets the outputs to 0.
When the power supply voltage exceeds 19.2 V, the voltage monitoring system waits for 16 ms before signaling and validating the outputs again.
A break in the power supply to the preactuators will not cause any internal fault to the module.