Siemens SIMATIC S7 System Manual page 683

Rated voltages
Table A- 7
Rated voltage
24 V DC
120/240 V AC
Note
When a mechanical contact turns on output power to the S7-200 SMART CPU, or any digital
expansion module, it sends a "1" signal to the digital outputs for approximately 150
microseconds. This could cause unexpected machine or process operation which could
result in death or serious injury to personnel and/or damage to equipment. You must plan for
this, especially if you are using devices which respond to short duration pulses.
Time duration for a mechanical contact to turn on output power
When a mechanical contact turns on output power to the S7-200 SMART CPU, or any
digital expansion module, it sends a "1" signal to the digital outputs for approximately 150
microseconds.
This can cause unexpected machine or process operation which can result in death or
serious injury to personnel and/or damage to equipment.
You must plan for this situation, especially, if you use devices which respond to short
duration pulses.
S7-200 SMART
System Manual, V2.3, 07/2017, A5E03822230-AF
Rated voltages
WARNING
Tolerance
20.4 V DC to 28.8 V DC
85 V AC to 264 V AC, 47 to 63 Hz
Technical specifications
A.1 General specifications
683