Canon SpeedLite ST-E2 Transmitter - a wireless transmitter designed to organize the operation of a maximum of two groups of slave flashes, while you can set the pulse power ratio of these groups in the range from 8: 1 to 1: 8. The range of 15-20 m indoors and 8-10 m outdoors.
The wireless E-TTL automatic flash control system can be used with other SpeedLite flash features, such as flash memory, strobe flash, etc.
To trigger the modeling light (it will work for 1 second, while the flashes will give out low-power light pulses with a frequency of 70 Hz), just click the button for assessing the depth of field on the device. If you use multiple flashes, the flashes will fire based on the set power factors.