Difference between Shunt Trip Left (STL) and Shunt Trip Flexible (STF)

Shunt Trip Left (STL)
Shunt trips type STL can be installed in the left-hand accessory pocket. These units are available with six different voltage ratings in the following range:
? 24 to 600 V AC 50/60 Hz
? 12 to 250 V DC

They have a maximum power consumption of 58 VA which is significantly lower than the power consumption of the flexible shunt trip versions. Switches (permanent signal) or momentary push-buttons (minimum signal duration 40 ms) may be used to control the shunt trips.

Shunt Trip Flexible (STF)
Shunt trips type STF can be installed in the left or right accessory pocket. They provide more flexibility for combining different auxiliary releases and even an under-voltage release in the same breaker.
The following voltage ratings are available:
? 24 to 600 V AC 50/60 Hz

Due to the design, the STF power consumption ranges up to a maximum of 750 VA and is therefore higher than the power consumption of STL versions.